Serves All the West

A History of Union Pacific Dieselization, 1934-1982

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This page was last updated on May 17, 2024.

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The information presented here is a greatly expanded and updated version from an original 1999 version used in Diesels of the Union Pacific, 1934-1982, The Classic Era, Volume 1, by Don Strack (Withers Publishing Co.)


Union Pacific's first Streamliner is its most famous early motorized passenger train. The celebrated train of 1934 was numbered M-10000 and was a yellow-and-brown lightweight passenger train, articulated and streamlined as a four-car trainset powered by a 600-horsepower oil-distillate internal combustion engine. Although it was intended for demonstration purposes and never meant for revenue service, that train and Chicago, Burlington & Quincy's diesel-powered Pioneer Zephyr--developed within a few months of each other--are generally regarded as the first internal-combustion-powered mainline intercity passenger trains in America.

Diesel-electric switchers had been working in the switching yards of American railroads since 1925, quietly racking up records for efficiency, economy, and availability. Even earlier, Union Pacific and other roads had used gas-electric cars for light branchline passenger service. One of UP's own officers developed the streamlined gas-electric vehicle design known as the McKeen car, which both UP and other railroads bought and used.

Internal combustion diesel engines first came to UP in the mid-1930s with the successor to M-10000, in the form of the road's second Streamliner, a lightweight articulated passenger train numbered M-10001. Separate diesel passenger locomotives began to appear with the arrival of the road's third Streamliner, M-10002, in 1936. The road tested diesel switchers in 1939, buying its first diesel switchers during the following year.

But mainline passenger and freight traffic remained in the steady hands of dependable, though costly-to-maintain, steam locomotives. In the 1920s and early 1930s on Union Pacific, this meant 2-8-2s, 2-10-2s, 4-12-2s, and articulated engines for freight service, and 4-6-2s and 4-8-2s for passenger trains. Until the arrival of M-10000 and the Zephyr, almost no one, inside or outside the railroad industry, knew for sure whether diesels could withstand the rigors of mainline service, not in passenger service and certainly not in freight service. M-10000, as it turned out, became the first in UP's fleet of passenger trains to which it gave the signature name "Streamliner."

During the late 1930s and early 1940s, Union Pacific management, in both the corporate and mechanical departments, became convinced that diesels could handle the more visible, yet lighter-duty, passenger trains, and they found that colorful, comfortable, fast new passenger trains were popular with the public. But they were equally convinced that only more and larger steam locomotives could meet the road's need for high-speed freight service. This was a reflection of the corporate culture these men had grown up in, from a time before World War I, when a better locomotive simply meant a more modern steam locomotive. The major (steam) locomotive builders embraced this thinking. Diesels were fine, they reasoned, but they would never attain the combined power and speed needed for freight service.

By 1945, UP was happy with the performance of its 175 modern steam locomotives, built in three designs --105 4-6-6-4 Challengers, 25 4-8-8-4 Big Boys, and 45 800-class 4-8-4s, all built since 1936 and among the finest examples of steam power ever built. The Big Boys developed 133,375 pounds starting tractive effort, which translated to approximately 6,300 maximum drawbar horsepower. Except for its high-public-profile Streamliners, Union Pacific came out of World War II as essentially a steam freight railroad. Its last steam engine was built in 1944, and by the end of 1946, the road owned 154 diesels -- 112 switchers and 42 passenger engines -- and not a single freight unit.

To obtain the same high performance from a diesel locomotive as it had from the Big Boy, Union Pacific, along with others in the railroad industry, figured it needed a double-unit locomotive (but preferably a single-unit locomotive), of the same 6,000-horsepower rating. (Many railroads embraced the philosophy of trying to replace steam engines one-for-one with equivalently powered diesels, resulting in many customized, non-standard, diesel-locomotive designs in those days.) Although UP had accumulated plenty of experience with its Streamliners and with much smaller gasoline- and distillate-powered self-propelled motor cars (owning a total of 58 cars), the latter all fell into the 200- to 300-horsepower range, much too small to be considered for freight service.

As the railroad looked proudly to its Big Boys, Challengers, and 800-class Northerns and pondered the future, one thing was quite clear. Every one of its competitors--the other major Western railroads--had already embraced the multiple-unit diesel concept for freight service, while UP had rejected it in favor of trying to find the self-contained diesel equivalent of the Big Boy. The multiple-unit "building-block" system, promoted by the Electro-Motive Corp., later the Electro-Motive Division of General Motors Corp.--employed varying numbers of units, all controlled from a single point, assembled for each run according to need, taking into account train weight, train speed, and a route's operating profile.

During the early and mid 1960s, UP was pretty deeply involved in working with EMD to push its 567 diesel engine to its limits. They kept GE and ALCO on the hook to encourage competition. This was the Double-Diesel era on UP. It was a combination of D. S. Neuhart's desire for improving locomotive technology, and Harold Rees as his chief design engineer. Then Rees retired in 1964, and Frank St. Lucas and Lloyd Edson took over his efforts. At about the same time, GM started work on their 645 engine, having pushed the 567 to its limits, i.e. the turbocharged 567D3 engine used in the DD35s and GP35. UP saw the potential of a high-horsepower 645 engine, and was among the first to buy EMD's SD45. In 1978, during a visit with Lloyd Edson, he showed a sketch for a double-engine version of the SD45; a monster at 7200 HP. But it was too long and too heavy. The old-head mechanical guys were retiring in the late 1960s, and the younger electrical guys were working on electrical solutions for a better locomotive. The result was that UP pushed EMD into Dash 2 technology, with the DDA40X Centennial locomotives as the test bed. Neuhart and UP were so confident in their guys' work that they bought a large fleet of Centennials, instead of just one, two or three test locomotives.

Across the ages, research has found that history, any history including locomotive history, is the story of the people doing the work, as much as the story of the technology. On Union Pacific, it was Otto Jabelmann that brought us the Challengers, Big Boys and 800s in the late 1930s and early 1940s. UP's president was William Jeffers, an old-head steam guy, and he held UP to its steam locomotives until his mandatory retirement in 1946. When George Ashby took his place as president, he took the path, any path, that Jeffers would never have taken. Hence UP's massive multi-million dollar order for diesel locomotives in 1946-1947. D. S. Neuhart took control of UP's mechanical department in 1949 and UP started its turbine era. Neuhart pulled Harold Rees into his office to design the ideal UP locomotive. While they pursued their designs for the super locomotive, they continued to buy multiple-unit sets from EMD and Alco to get their ideal 6000HP locomotive, matching the power of a Big Boy. This 6000HP number keeps popping up in all the correspondence, with the pinnacle being the 6600HP DDA40X of 1969. Then in 1971, Neuhart retired and his replacement, Frank Acord, was told to only buy what was was available from the builders, and that UP was no longer in the business of designing locomotives. This was the dawn of the SD40-2, the most successful locomotive in all of railroad history. And UP's fingerprints are all over the SD40-2, based on what was originally part of the DDA40X Centennials. In 1980, just before the UP-MP-WP merger, UP was going to buy another large fleet of SD40-2s, with some improvements. The longest-lasting feature of this planned order was what has become known as the heavy-block 645, a UP improvement to strengthen the engine. SD40-2s, with heavy-block 645 engines, are in high demand even today, many, many years after they were built.

For good or bad, Union Pacific was always on the cutting edge of railroad technology, and most other railroads chose not to follow, for a variety of reasons. But there is still a debate to be had about UP's constant search in the late 1930s through the mid 1960s for the ideal locomotive. Other than being unique in its locomotive designs, making for some significant railfan favorites, was the money well spent in terms of moving tons of freight from point 'A' to point 'B'? Other historians have written that UP continued to make gobs of money in spite of everything they did, due to the high value of the Overland Route. One has to wonder what the company's financial reports might have been if UP hadn't spent so much money and other resources looking for the ideal single-crew/single-unit locomotive, and simply used more of whatever the other railroads were using.

Early Internal Combustion Motor Cars

The first internal-combustion rolling stock on UP was a series of self-propelled McKeen passenger cars, powered by small gasoline and distillate-fueled engines. These motor cars were designed by UP's superintendent of motive power and machinery, William McKeen, and were built beginning in 1905 by UP in the railroad's Omaha, Nebraska, shops. In 1908, UP organized the McKeen Motor Car Co. as a subsidiary to sell McKeen cars to other railroads, and production continued in the Omaha shops. With their distinctive wedge-nosed front ends, these cars were designed and operated as self-contained passenger trains, but by 1909, they were powerful enough to pull a trailer.

Competition for McKeen's mechanical-transmission motor cars came in 1911 when General Electric released its own design for an electric-transmission motor car. McKeen's largest vehicle, a rounded-front 300-horsepower car with a three-axle power truck, was completed in 1916 as a demonstrator for Southern Utah Railroad in Utah's Carbon County coal fields (it was delivered on January 1, 1917). The last McKeen cars were completed in 1917, which was also GE's last year for motor-car production. The production of motor cars ceased with the United States' entry into World War I. By 1920, McKeen's mechanical-transmission car had lost sufficient interest among potential customers that UP bought full control of McKeen and formally stopped production. Union Pacific completed several motor cars for itself during mid-1923, using the remaining McKeen bodies.

A growing interest for electric-transmission motor cars after the war led to the formation of Electro-Motive Corp. in 1922 to again market gas-electric motor cars to America's railroads, taking advantage of better and more powerful engines and better electrical control. In 1927, UP began buying Electro-Motive motor cars, receiving 15 cars during 1927 and 1928. Also in 1928, UP acquired two motor cars from Brill, and another two came from Brill in 1930. Several of the mechanical McKeen cars were converted to gas-electrics during the 1920s, and the last mechanical McKeen cars were retired in 1942. Electric-transmission motor cars with both gasoline engines and distillate engines remained in service on UP throughout the 1940s and 1950s, with the last one being retired in 1961.

Between 1920 and 1932, the number of passenger-miles for America's railroads had dropped by two-thirds, inversely matching the tripling of automobile registrations during the same period. The public wanted faster schedules and more comfort. To furnish faster schedules, Union Pacific needed either lighter trains or more powerful locomotives. UP chose to pursue a lighter train, based on its experience with self-propelled motor cars, with their electric transmissions and increasingly powerful distillate engines during the late 1920s. Lighter trains would also spring from developments in lightweight metals during the post-World War I years, and from aerodynamic designs for rail equipment (specifically, Pullman's Railplane of March 1933). More comfort, especially for business and upscale pleasure travelers, would come with new, more modern designs. These developments led Union Pacific in 1933 to ask for the development of the lightweight, articulated passenger train, which became known as The Streamliner. Union Pacific saw The Streamliner as the answer to what the traveling public wanted, and the first Streamliner was M-10000.


Union Pacific's first internal-combustion locomotive was actually the power car of an articulated passenger train. M-10000 was built as the first streamlined passenger train in North America, and was equipped with a 600-horsepower Winton distillate engine, very similar to the engine used two years before in Santa Fe's M-190 articulated motor car. Union Pacific's M-10000 train featured an all-aluminum, wind-tunnel-tested tubular carbody design that marked the beginning of the streamlined era on America's railroads. Concurrent streamlining efforts included Chicago, Burlington & Quincy Railroad's number 9900, the Pioneer Zephyr, completed just two months after M-10000, as the first diesel-powered streamlined passenger train in North America. Pennsylvania Railroad's experimental streamlined pair of electric locomotives, GG1-class 2-C+C-2 unit 4899 and R1-class 2-D-2 unit 4800 (they later traded road numbers as the GG1 design entered mass production) was completed in August 1934, six months after UP M-10000.

UP formally placed its order with Pullman in May 1933, using the proven Winton Engine Co. distillate engine. Three weeks later, in mid-June, Burlington placed the order for its streamlined train, with Winton's new 201-A diesel engine, of which only two small prototypes, and no production versions, had been completed. Both streamlined trains were originally intended to be diesel-powered, but Pullman finished the all-aluminum UP train first, and the new Winton diesel was not yet ready, so UP settled instead on the earlier Winton 191-A distillate engine. Union Pacific's 600-horsepower, three-car, articulated train was ordered from the Pullman Car Co. on May 24, 1933, and was under development and construction between that date and its completion date more than eight months later, in February 1934. (In 1934, the Pullman Car & Manufacturing Co. combined with the Standard Car Co., becoming the Pullman-Standard Car Manufacturing Co., commonly known as Pullman-Standard.)

M-10000 was constructed as an engineering development vehicle to demonstrate the practicality of long-distance, lightweight passenger trains. Early in 1933, Union Pacific set aside $200,000 for the construction and operation of such a train to gather engineering and operating data that could be used in the design and construction of larger trains for revenue service. Unlike CB&Q, which built its Pioneer Zephyr with a particular service and route already planned, Union Pacific had Pullman build the M-10000 as an experimental demonstrator with no market in mind. With seating for only 116 people--about 1-1/2 times that of a single heavyweight coach of the day--its capacity was extremely limited. To recover some of the costs of its development, UP eventually assigned the train to the 187-mile Kansas City, Missouri, to Salina, Kansas, portion of its Kansas City-Denver route after it proved the success of the lightweight train concept.

The train was delivered to Union Pacific on February 12, 1934, and set out on a nationwide tour until late 1934, including a two-month display at the Century of Progress International Exposition in Chicago. The train returned from its national tour and entered revenue service on January 31, 1935 operating as The Streamliner. The name was changed to City of Salina on March 13, 1935. During 1937 and 1938, it left Salina, in central Kansas, at 7 a.m., heading east, and reached Kansas City at 10:30 a.m. Half an hour later, it was ready to head west again, running as far as Topeka, 68 miles, in just 68 minutes. Turning again, it left Topeka at 12:30, getting back to Kansas City at 1:38--another mile-a-minute average speed. Then it left Kansas City at 4 p.m. (5 p.m. in 1938) and tied up at Salina at 7:30 p.m. (8:30 p.m. in 1938). On the 187-mile Salina-Kansas City run, its elapsed travel time was 3-1/2 hours, with 10 intermediate stops. This was 70 to 75 minutes faster than the best steam-powered express on the route, the heavyweight Pacific Limited, which made fewer stops.

M-10000 was removed from service on December 16, 1941, after six years and 900,000 miles of revenue service, and was sold for scrap to Aaron Ferer and Sons in Omaha, Nebraska, on February 13, 1942.

EMD later assigned model numbers to M-10000 and to Burlington's Pioneer Zephyr, using the model AA to denote, "Passenger A unit with baggage compartment. Noted diesel locomotive historian John Kirkland has referred to these power units as "baggage-car locomotives."


Following M-10000 came the M-10001. Actually, two trains were numbered as M-10001. The first M-10001 was a 900-horsepower, six-car fully articulated train, and the first Pullman-sleeper-equipped streamlined passenger train in North America, and Union Pacific's first diesel-powered train. The power car was built by Pullman-Standard (as part of the entire train) and powered using a Winton diesel engine, a General Electric generator, and four General Electric traction motors. The larger M-10001 was ordered from the Pullman Car & Manufacturing Co. on June 30, 1933, one month after M-10000, and just two weeks after Burlington's 9900 was ordered from Budd. M-10001 was under development and construction (including improvements discovered from the operation of M-10000) between its order date and its completion date 15 months later, in September 1934. It was delivered to Union Pacific on October 2, 1934 and toured the United States for display and testing purposes over the next two months. Without its having rolled a single mile in revenue service, UP in December 1934 returned the entire train to Pullman for remodeling and improvement to increase its power and capacity.

The original M-10001 was a 376-foot-long, fully articulated six-car train. It included the 48-foot turret-cab power unit, a Railway Post Office/baggage car, three Pullman sleeping cars, and a round-end coach/buffet car. The remodeled M-10001 was a 455-foot-long, seven-car train. The remodeled train included the 60-foot, three-inch turret-cab power unit (increased by 12 feet to accommodate the larger 1,200-horsepower, 16-cylinder engine), a Railway Post Office/baggage car (increased by eight feet to accommodate a steam generator compartment), a diner/lounge car, three Pullman cars, and a round-end coach/buffet car.

This remodeled M-10001 was equipped with the first production 16-cylinder 1,200-horsepower Winton diesel engine. The new engine replaced a prime mover that itself had represented a previous first--the first installation of Winton's 12-cylinder 900-horsepower diesel engine, both being installed within a seven-month time span.

Pullman delivered the remodeled M-10001 to Union Pacific on May 23, 1935, in a ceremony at the Chicago & North Western Railway's station in Chicago. (C&NW handled the eastern 491-mile leg of UP's transcontinental passenger service between Omaha, Nebraska, and Chicago.) The train made three test runs between Omaha, Nebraska, and Portland, Oregon, during late May, and was dedicated at the Portland Rose Festival as the first City of Portland on June 5, 1935, entering revenue service the next day when it left Portland on its maiden trip to Chicago.

The second M-10001 remained in service until June 1939, when the train was replaced in City of Portland service by the M-10002 trainset, which had been reassigned from City of Los Angeles service. The 900-horsepower Winton diesel engine and other power equipment from the power car, and the steam generator from the RPO/baggage car, were salvaged by UP in December 1939 and installed in a new carbody (built by Pullman-Standard) that entered City of Denver service as CD-07-C, as additional motive power to support increased schedules and train consists on that train's Chicago-to-Denver route. M-10001 remained stored for two years (without its diesel engine after December 1939), until it was retired and sold for scrap on August 13, 1941.

Electro-Motive company records show an earlier M-10002 and M-10003, to be built after the M-10001. Both were ordered during November 1933 (M-10000 was ordered in May 1933 and M-10001 was ordered in June 1933). The first M-10002 and M-10003 were originally intended to enter service as the initial City of Los Angeles and City of San Francisco, and were also to be designed and built as articulated trainsets similar to M-10000 and M-10001. The two trains were given Pullman-Standard lot number 6433. EMC assigned a common order number, E121, to M-10001, M-10002, and M-10003. M-10001 was built; these earlier versions of M-10002 and M-10003 were not.

Using lessons learned during the operation of both M-10000 and M-10001, Union Pacific and Pullman-Standard returned to the design table for additional horsepower to pull the increased number of cars of the proposed new trains. In an effort that would confuse later historians, EMC canceled the remaining units in order number E121 in December 1934 and assigned a new order number (E131) to the newly redesigned M-10002, delivered in April 1936, but Pullman-Standard retained its lot number 6433 for the new M-10002 train. The redesigned M-10003 was later delivered in July 1936 as a spare locomotive set of an entirely different carbody design, being part of the City of Denver order, using Pullman-Standard lot number 6484, and EMC order number E132.

Following the May 1935 delivery of Union Pacific's remodeled M-10001, EMC produced five boxcab passenger locomotives. EMC contracted with General Electric to complete two of the five units in June 1935 for demonstration purposes. A contract with St. Louis Car Co. completed the third in August 1935 as Baltimore & Ohio number 50. The fourth and fifth were also completed in August 1935, also under contract to St. Louis Car Co. These two units were Santa Fe's semi-streamlined 1A and 1B, used on an entirely new train, the heavyweight Super Chief between Chicago and Los Angeles, which made its inaugural run in May 1936. These five locomotives were EMC's first separate passenger locomotives that were capable of directly replacing steam locomotives. They were of heavyweight sheet steel and cast-steel construction, and rode on two two-axle trucks. Each was equipped with twin 900-horsepower 12-cylinder Winton diesel engines, giving them each an 1,800-horsepower rating. Design improvements from these units were incorporated UP's next Streamliner, M-10002.


UP's third Streamliner was M-10002, completed in late April 1936, and was the last of the turret-cab Streamliners. It was also the first stand-alone diesel locomotive on UP. The train entered service as the City of Los Angeles on May 15, 1936, the day after Santa Fe's new heavyweight Super Chief had made its initial run between the same two cities. As with the previous M-10000 and M-10001, Pullman assembled the M-10002, but it was more powerful than the two earlier designs, being equipped with a 1,200-horsepower lead unit and a 900-horsepower booster unit, with nine cars. The three-car M-10000 had been powered by a 600-horsepower prime mover and the six-car M-10001 had been powered by a 1,200-horsepower prime mover.

The 900-horsepower, 12-cylinder diesel engine used in the M-10002 booster was the same one that UP had removed from the earlier M-10001 when it was rebuilt to a 1,200-horsepower rating. M-10002 was changed from City of Los Angeles service to City of Portland service in December 1937. It was stored from July 1941 to April 1942, when it was assigned to a Portland-Seattle connection. It was stored again in March 1943, and its cars were removed.

The power cars were finally retired in December 1946 and sold to Northrop-Hendy Company, a joint venture of Northrop Aircraft Company and Joshua Hendy Company formed to advance the development of turboprop aircraft engines. Union Pacific's president William Jeffers cooperated with Northrop-Hendy in studies of using the company's Turbodyne 10,000 HP aircraft engine for non-aircraft purposes. The experiment to use the turboprop engine for non-aircraft purposes was abandoned after GE bought the Hendy turboprop design patents, and the two-unit set of locomotives sat on a spur at Northrop Aircraft's plant at El Segundo, California, until they were scrapped in December 1947. (Trains magazine, October 1957, page 25, with photo)

(Read more about the Northrop-Hendy turboprop project)

M-10003 to M-10006

In May, June, and July 1936, Union Pacific received four identical power sets, numbered as M-10003, M-10004, M-10005, and M-10006. The lead unit of each of these locomotives featured a then-new "automobile-design" elevated cab. Although each unit had two two-axle trucks, the rear power truck of the lead unit shared a span bolster with the lead truck of the booster unit, forming a 2,400-horsepower locomotive from the 1,200-horsepower lead unit and the 1,200-horsepower booster unit. One power set was assigned to the City of San Francisco, two were assigned to the new City of Denver, and the fourth set was used as a spare and was operated on either of the two other routes--from Chicago to Denver, or from Chicago to San Francisco. Earlier, a nearly identical power unit had been completed by Pullman, in March 1936, for Illinois Central as that road's number 121, used on IC's Green Diamond streamlined train between Chicago and St. Louis.

The first of these four locomotives to be completed for UP was M-10004, finished in May 1936, a month after the turret-cab M-10002. While the power units of M-10004 had vertical carbody sides, the train itself retained the tapered-side design of the three earlier Streamliner trains. M-10004 was the first City of San Francisco, and entered revenue service on June 14, 1936. Just 18 months later, in January 1938, M-10004 was replaced by the new E2-powered SF-1, -2, -3. Following a thorough refurbishing by UP's Omaha shops, during which it was renumbered to LA-4, the train in July 1938 entered City of Los Angeles service, replacing M-10002, which in turn replaced M-10001 in City of Portland service. After less than a year, in March 1939, the LA-4 was replaced by new EMC E3s, numbered LA-5 and LA-6. In June 1939, the LA-4 lead unit was rebuilt as a booster unit, renumbered to CD-06-C, and assigned as additional power to the City of Denver trains to support that Streamliner's increased train size and expanded service. The LA-4 booster unit was renumbered to CD-05-C, and also entered City of Denver service. Both units were retired and scrapped with their respective power sets in 1953. (A third booster unit for the City of Denver trains, CD-07-C, was completed using a new carbody and the power equipment from M-10001 in December 1939.)

M-10005 and M-10006 were completed in June 1936 and entered service as the new City of Denver trains on June 18, 1936. After operating for a year, accumulating 765,000 miles and moving more than 129,000 passengers between Chicago and Denver, the two "Denver twins" were renumbered to CD-5 and CD-6 in June 1937.

Completed as a spare locomotive set in July 1936, the fourth of these new power sets, M-10003, was intended to protect the motive power needs of both the City of Los Angeles and the City of San Francisco. In June 1937, it was assigned to the City of Denver and renumbered to CD-07. It remained in City of Denver service for 16 years until it was retired in March 1953. It was scrapped by UP at Omaha in mid-1953.

The three City of Denver power sets, CD-05, CD-06, and CD-07 (the former M-10005, M-10006, and M-10003) remained in that service until the City of Denver trains were re-equipped with modern lightweight equipment from the general equipment pool and E8 locomotives in 1953. All three trains and their distinctive locomotives were scrapped by UP at Omaha during the summer of 1953.


Electro-Motive continued to refine its design for a stand-alone passenger locomotive, based on what it had learned with the five 1,800-horsepower B-B (two two-axle trucks, with all axles powered) boxcab units it built for Santa Fe and B&O, and the two demonstrators, all completed between the delivery of M-10001 in May 1935 and the delivery of M-10002 in May 1936. One of the lessons was that the two-axle trucks did not operate well at high speeds, especially when entering curved trackage. Another major lesson was that these high-speed locomotives needed to be streamlined, similar to the M-10003 to M-10006 power sets delivered to UP in May to July 1936.

EMC's answer to these two problems was the model EA locomotive, introduced in May 1937, with six cab units and six booster units being supplied to B&O, and the E1 locomotive introduced in June 1937. (The model designation "E" stemmed from the original powering at Eighteen-hundred horsepower.) Eight E1As and three E1Bs were delivered to Santa Fe. These two designs were streamlined, and both were equipped with EMC's new three-axle, A1A passenger truck (two powered outboard axles, with the center one unpowered). The truck was designed by Martin Blomberg, who, as an employee of Pullman in 1934, had participated in the patent for the streamlined design of UP's M-10000. By 1937, Blomberg had moved to Electro-Motive. He was also involved during early 1938 in solving the B-B truck tracking problem on Santa Fe's two earlier boxcab units, 1A and 1B, by adding an unpowered axle ahead of the two powered axles. Also in 1938, he designed the leaf-spring, swing hanger-equipped, arch-sideframe two-axle truck that was first applied to EMC's FT freight locomotive.

In October 1937, following the construction of the first EAs for B&O and the first E1s for Santa Fe, EMC furnished Union Pacific with two A-B-B sets of E2 locomotives for its newly expanded, 14-car City of San Francisco and City of Los Angeles trains. As with the EAs, built only for B&O, and the E1s, built only for Santa Fe, these E2 locomotives were built only for Union Pacific. Although they were mechanically similar to the EAs and the E1s (with twin 900-horsepower diesel engines and A1A trucks), the E2s featured a much different exterior design. The EAs and E1s shared recessed headlights and smooth sloped noses, but the E2s boasted bulbous noses with prominent headlight casings, and much automobile-like chrome trim work.

The City of San Francisco A-B-B set of EMC E2s, initially numbered as SF-1, SF-2, and SF-3, were owned jointly by Union Pacific, Southern Pacific, and Chicago & North Western. The comparable City of Los Angeles set, numbered as LA-1, LA-2, and LA-3, was owned jointly by UP and C&NW. This shared ownership reflected the shared operation of these two trains over each road's route: for the City of Los Angeles, from Chicago to Omaha, Nebraska, via C&NW, and from Omaha to Los Angeles, via UP; and for the City of San Francisco, from Chicago to Omaha, via C&NW; from Omaha to Ogden, Utah, via UP; then from Ogden to Oakland, California. (San Francisco), via SP. Shared ownership was seen as the best way to control equipment usage and the costs of operation and maintenance of equipment dedicated to the Streamliner trains. The outward evidence of joint ownership was reflected in the separate emblems attached to these E2 locomotives, and to the earlier City of Denver units.

The EMC E2 A units remained in their respective assignments from their construction in 1937 until the joint ownership agreements were terminated in 1948. The former SF-1 (renumbered to 901A, then 983J) was sold to SP and became that road's number 6011A. The former LA-1 (renumbered to 921A, then 984J) was sold to C&NW and became its number 5003A. The four E2 B units remained in their respective assignments until they were retired and traded to EMD on new E8s in 1953.

These two new E2 5,400-horsepower locomotives would soon prove that diesel locomotive technology could now compete with steam locomotives on the railroad's fastest and heaviest passenger trains. Six months before the delivery of the E2s, advocates for steam locomotives on UP countered the growing acceptance of diesel Streamliner trains in April 1937 with two streamlined steam locomotives, 4-8-2 Mountain 7002 and 4-6-2 Pacific 2906. These two locomotives were first used in July 1937 to power the new all-Pullman Trains 48-49, The Forty-Niner, between Omaha, Nebraska, and Ogden, Utah, where the train was handed off to Southern Pacific to continue its journey to Oakland, California.

GE Steam Turbines

For a brief period from early April through mid June 1939, UP operated a two-unit, 5,000-horsepower steam turbine-electric locomotive built by General Electric. The pair of locomotives were completed in December 1938 and delivered to UP at Omaha, Nebraska, on April 3, 1939. Union Pacific historians William Kratville and Harold Ranks described the promise of the pair, writing that the steam turbines "were lauded as replacement to steam; successor of diesels."

The two locomotives were on Union Pacific as a 60-day demonstration by GE and Babcock-Wilcox, the manufacturer of the steam turbines themselves. UP was willing to run the locomotives to see if they were comparable to the modern 4-6-6-4 Challenger freight steam locomotives UP had received in 1936-1937, and the 20 4-8-4 Northern passenger steam locomotives had received in 1937, and the 15 passenger 4-8-4 Northerns UP had on order for delivery in August 1939.

The concept of steam-turbine locomotives was presented to UP by General Electric in late 1936, and with UP wanting to try alternatives to steam and the new diesel passenger locomotives, the two companies began development efforts. Just six months before, UP had received the four 2,400-horsepower Pullman-built locomotive sets (M-10003 to M-10006) as part of the newly re-equipped City of San Francisco and City of Los Angeles. The road had also just received 15 new 3900-class 4-6-6-4 Challenger steam locomotives, with 25 more to be delivered in 1937. In addition, 20 new 800-class 4-8-4 Northerns were to be delivered during 1937. The road's mechanical and operating departments were anticipating being able to compare the performance of the most recent examples of locomotive technology -- steam, diesel, and steam turbine.

Numbered UP 1 and 2, the two steam turbine units each generated 2,500 horsepower, and burned oil to produce the steam for the units' turbines. Built by GE under contract to Union Pacific, they were the first railway turbine locomotives built in North America. They also represented GE's only attempt at steam-powered locomotives. The two locomotives were under construction during most of two years, with a final build date of December 1938, although a photograph of the erecting bay at GE in Erie, Pennsylvania, dated December 24, 1937, shows them about 95 percent completed. Both units were tested extensively on GE's test track at its Erie plant until final road testing, which took place on New York Central from January through March 1939.

These two locomotives had condensing turbines using water tube boilers and advanced combustion automatic controls including feedwater for the boilers. These controls were furnished by Bailey Meter Company from Cleveland, Ohio. The loco boilers were furnished by Babcock and Wilcox from Barberton, Ohio. (Richard Browngardt, a retired employee of Bailey Meter Company, email dated September 9, 2013)

The two locomotives worked their way to Council Bluffs, Iowa, over NYC and Chicago & North Western, and as noted, were delivered to UP on April 3, 1939. During April, they operated in several test and publicity trains between Cheyenne and Laramie, Wyoming, between Cheyenne and Denver, and from Cheyenne to Salt Lake City and Los Angeles. They were part of a publicity photo taken in late April in Los Angeles for the grand opening of the new Los Angeles Union Passenger Terminal, planned for May 1, 1939. They departed Los Angeles on April 24th and returned to Omaha with a special train of celebrities and were displayed near that city's downtown on April 27, 28, and 29, 1939, during the world premiere of Cecil B. DeMille's epic film "Union Pacific" on April 28.

During the first two weeks of May 1939, the pair completed a whirlwind movie promotion tour of the eastern states for Paramount Studios, including an exhibition for President Franklin D. Roosevelt. They returned to UP and made several trips as separate units on passenger trains between Omaha and Denver. On June 5, 6 and 7 the two locomotives were reunited and used to take the Paramount movie special back to Los Angeles, arriving 2 hours and 26 minutes late due to several road failures. The road failures resulted in just one of the two locomotives being online on several locations along the route, which in-turn resulted in the need for helper locomotives on grades in Wyoming, Utah and Nevada where helpers were not normally needed. Additional failures took place on the return trip to Ogden on June 8 and 9. However, at Ogden, the mechanical people accompanying the locomotives had enough confidence that the locomotives were used as the sole motive power on a special 1,100-ton block of 18 refrigerator cars known as the Cherry Fruit Special. The trip across across Utah and Wyoming, and continuing eastward across Nebraska to Council Bluffs was relatively uneventful, arriving on June 11th. The normal schedule for the Cherry Fruit Special, Ogden to Council Bluffs, as 23 hours 10 minutes. This trip took 34 hours 20 minutes due to delays not associated with the locomotives.

Despite all of the high-profile activity in April and May and June, the tests had shown that the steam turbine concept was not quite ready for railroad service, due mostly to the units' low reliability and increased maintenance. Several road failures had occurred, to the point that Union Pacific management was not satisfied with the reliability of the two unique locomotives. Simply put, the two units were unsuccessful during UP's tests in long-haul service and never entered regular revenue service.

The locomotives were returned to General Electric at Erie on June 17, 1939, via Chicago. Representatives from both UP and GE continued to work for another 2-1/2 years at improving the units' reliability, with cold-weather tests taking place on New York Central. A February 1941 report by a UP staff engineer was positive in its contents, but by the end of 1941, it was obvious to UP that the design was not what the railroad wanted. On December 18, 1941, UP President William Jeffers notified GE that the railroad had no further interest in the project, citing increased costs and improvements in other railroad motive power (such as EMD's pioneering FT locomotives). In December 1941, UP took a charge of $73,276.73 to write-off the costs of the failed program.

After UP pulled out of the project, the units were repainted dark gray and renumbered to GE 1 and 2. During 1943, they were leased to Great Northern Railway for nearly a year for wartime short-haul freight service in Washington, performing without a major failure. By late 1943, they were returned to GE and retired.

In a letter to the editor in the February 1970 issue of Railroad magazine, an old General Electric locomotive man, F. H. Craton of Erie, Pennsylvania wrote:

On May 10, 1943, when I was working on industrial locomotive sales out of Erie, I rode the steam turbine-electric which had been delivered to the Union Pacific in 1938, between Spokane and Wenatchee on the Great Northern. Here is an excerpt from the diary I kept on that trip:

"When we got to the station, we found the steam-electric already there and about to back in on No. 27, a six-car mail train westbound. Floyd Gowans (GE) and Mosher of Babcock & Wilcox were on her. It was very informal; I just got aboard--no pass, no ticket, no release, no nothing--but everyone assured me it was OK. They have christened the locomotive 'The Jeep,' and the GE men with her were known as technical sergeants.

"We pulled out at 7:18 p.m. for Wenatchee, 178 miles away. We climbed the long hill west of Spokane like it wasn't there at all. Then we more or less drifted most of the way from there on, occasionally using the rheostatic brake, which the engineers love. The speed fooled the fireman; he consistently underestimated it by 10 to 15 mph.

"Soon it was dark. Great Northern's signal system gave me the jitters a few times. If the green blinked at you, it meant you were approaching a restrictive signal. We got several blinks. Sailing along a single-track crooked line at 70 to 75 mph in the dark kind of made me uneasy, as the engineer usually made no move to slacken speed. On one occasion, we got a blink and then a yellow; but he kept going plenty fast until the red eye actually appeared and it didn't look very far away either. However, he pulled her down very nicely before we got there.

"The trip was made alternately in full moonlight and then sharp squalls. As we approached the Columbia River, we got into some rugged country, running through deep cuts, tunnels and sharp curves until we finally swung around onto the river. During the trip, the fireman regaled me with numerous rattlesnake stories until I doubt if I would have dared put a foot on the ground anywhere except in a station. We arrived in Wenatchee on time shortly after eleven.

"As I had ridden this loco for the first time, out here on the rather God-forsaken job, I felt a great desire to see us make something of this thing. Here was the loco that F. D. Roosevelt came out to see once--now it is out here forgotten by all but the faithful few who have lived with it for six years now, damned discouraging years at that! Maybe tonight the steam-electric won someone else to its cause.

"Mosher, too, has lived with this job since the beginning and is just full of it. He poured out his optimism about our ability to produce an infinitely better loco if we were to make another. The skeptic almost had me sold on it. Maybe one day we shall cash in on this costly experience--who knows?"

My feeling about this locomotive had been that, among other problems, it was so enormously complex that there was difficulty keeping everything functioning properly at the same time. It was interesting, therefore, that when I congratulated Mosher on a perfect trip that night, he told me there had been a couple of minor failures, which he had been able to correct so quickly that nobody was aware of them.

(See also: "The Steam-Turbine-Electric Story" by Thomas R. Lee, in The Streamliner, Volume 10, Number 2 [1995], for an excellent 22-page article about these unique locomotives.)

Early 1940s Motive Power Numbering

For passenger locomotives purchased in 1940 and after, and intended for UP's exclusive use on its non-jointly-owned Streamliner passenger trains, UP devised a unique numbering system used to identify the "Motor" sets of locomotive units, in much the same way that the early motor cars and the early Streamliners carried an M- prefix to their road numbers. Thus, the six new, solely-UP-owned E6 units delivered in August 1940 were numbered as the seventh (7-M), eighth (8-M), and ninth (9-M) passenger train motor sets. E3A LA-5 and E3B LA-6, delivered in March 1939, became the fifth (5-M) motor set in February 1941.

As conjecture, the first and second motor sets (1-M and 2-M) would likely have been the City of Los Angeles and the City of San Francisco three-unit, 5,400-horsepower locomotives SF-1, -2, and -3, and LA-1, -2, and -3. The third and fourth, and sixth, motor sets (3-M, 4-M, and 6-M) might have been assigned to the three City of Denver three-unit, 3,600-horsepower locomotives. No documentation has been found that assigns specific motor-set numbers to any of these locomotives, however, their quantities match the apparent general numbering scheme.

On the E3 A and B set and the six E6As that did receive motor-set numbers, the first and second part (unit) of each set was designated with either a -1 or a -2, as in 5-M-1, 5-M-2, 7-M-1, 7-M-2, 8-M-1, 8-M-2, and 9-M-1 and 9-M-2. The A and B suffixes for the A-units and the B-units were added in much smaller lettering on the units themselves to show the differences in the type of unit, although the only B-unit involved was E3B 5-M-2B, the former LA-6. The two E7As (959A and 960A) and three E7Bs (961B, 962B, and 963B) delivered in August 1946 were originally ordered in the motor-set number series, as the tenth (10-M-1A and 10-M-2A) motor set and as additional units for the seventh (7-M-3B), eighth (8-M-3B), and ninth (9-M-3B) motor sets. The very confusing motor-set numbering scheme was changed at the time of delivery of these five E7s in August 1946, and they were delivered in the then-new 900 series assigned to UP's passenger locomotives.

Unfortunately, research has not turned up the reasoning behind the railroad's decision to number its Fairbanks-Morse Erie-built freight locomotive set, delivered in 1945, as 50-M-1A, 50-M-2A, and 50-M-3B. Possibly, the "50-" number series was chosen to allow plenty or room for expansion in the passenger series, since the Erie-built locomotives were purchased as a combination freight and passenger locomotive, only later to be assigned solely to passenger service. They were changed to passenger service about six months after delivery, after having proved themselves unsuitable for freight service.

Early E Units on Union Pacific

Union Pacific's two E3 units (a single cab unit and a single booster unit) were the first production units of that new model, completed in March 1939, six months after the E3 demonstrator was completed in September 1938. The two units were delivered in UP's then-current scheme of Armour Yellow and Leaf Brown (which was later replaced by the now-standard Harbor Mist Gray). Their numbers were LA-5 and LA-6, reflecting their assignment to UP's City of Los Angeles streamliner train. When the streamlined City of San Francisco was wrecked at Harney, Nevada, in August 1939, the two E3s were re-assigned to the temporary replacement train, along with the equipment from the original City of San Francisco (displaced in 1937), and operated on that route until the original E2-powered train was returned to service. At that time, the two E3s were placed into UP's general passenger power pool and used as needed on any of road's passenger trains. In February 1941, with the delivery of new E6s for the new City of Los Angeles train, the two E3s were renumbered to 5-M-1A and 5-M-2B, matching the new number series for non-Streamliner trains.

In August 1940, 18 months after UP received its two E3 locomotives, and as the road continued to convert its passenger trains from steam power to the new diesel power, it received six E6s. These new units were numbered in the new non-Streamliner number series of 7-M-1, 7-M-2, 8-M-1, 8M-2, 9-M-1, and 9-M-2. All six units were assigned to the road's Eastern District trains, and also served as spare locomotives for the City trains.

Possibly the most notable fact about UP's E6s is that they were the first units delivered with the new Streamliner colors of Armour Yellow and Harbor Mist Gray, a color scheme that has lasted almost 60 years, and which today remains as UP's trademark colors. In 1946, these six units were renumbered to 953A-958A, and in 1948, they were renumbered to 992-997. As UP continued to modernize its passenger power fleet, these six E6s were traded to EMD in 1956 for new E9s.

Six more E6s were delivered in February and March 1941, when the service of both the City of Los Angeles and the City of San Francisco were increased from five departures per month to ten departures, using completely new equipment. Each new train was equipped with 14 new cars, and a set of new E6 locomotives. The previous numbering system was continued, making the new power sets LA-4, LA-5, and LA-6 for the additional City of Los Angeles train, and SF-4, SF-5, and SF-6 for the added City of San Francisco train. These new units also carried the new Streamliner colors of yellow and gray, as did their accompanying new trains.

The general renumbering of UP's passenger motive power in 1946, with the delivery of new E7s, changed the numbers of the two E3s from 5-M-1A and 5-M-2B to 951A and 952B. In 1948 they were renumbered to 991 and 992B. They were retired in 1956 and used as direct trade in units for new E9s 901 and 904B.

The E6s were also renumbered in 1946, from SF-4, SF-5, and SF-6 to 904A, 905B, and 906B, and from LA-4, LA-5, and LA-6 to 924A, 925B, and 926B. All were again renumbered in 1948 to jointly-owned 985J, 985BJ, 985CJ, 987J, 987BJ, and 987CJ. With the end of joint UP/C&NW/SP equipment ownership at the end of 1948, the 985J became C&NW 5004A as part of the final equalization. The remaining five units became 985B, 985C, 987, 987B and 987C. All were traded to EMD in 1956 on new E9s.

"I have found no instances of a trailing A-unit on a 'City" train before 1958. Not to say it didn't happen, just that it was not common. Also, the most common motive power was A-B-B sets of E-units. That includes mixes of E-2's, -3's, -6's,  and -7's, as well as matched sets." (Dick Harley, email dated May 4, 2000)

"The earliest photo I've found of an E6 A unit with the angled number boards and the second headlight (except for the "City" train E6 cabs, which always had two headlights), is of the 993 on page 195 of Don Strack's "Diesels of the Union Pacific, Vol. 1." That photo, dated June 1949, also shows that the side windows have been replaced by carbody air filters, though not exactly - there are more filters than there were windows, and they aren't in exactly the same places. The same book has a photo of the 987 on page 193 with all the same modifications, but it isn't dated. However, since the unit is shown leading a pair of E8 boosters it must be at least June 1950 if not later. The E6 boosters don't seem to have received the carbody filter modification, at least not by 1951 (photo on page 202 of Don's book). However, they all originated as boosters in the "City" train power sets, so they had the 2-2-2-1 window configuration. Model B units with the 1-2-2-1 windows are a good match for the UP's E7 boosters." (Andy Sperandeo, email dated June 7, 2000)


The production of EAs, E1s, and E2s by Electro-Motive in 1937 served to further refine the builder's design for stand-alone diesel locomotives. Each of these three models used a pair of 900-horsepower Winton 201A diesel engines and General Electric electrical gear. In 1935, EMC completed a new factory at LaGrange, Illinois, near Chicago. Previously, the firm had been located in Cleveland, and had contracted with other builders to assemble its locomotive and motor-car designs. The move to LaGrange allowed EMC to pursue its own diesel engine designs, and designs for its own electrical gear.

By mid-1938, these new engine, generator, and traction-motor designs were ready for production. To make use of these new designs, EMC began design and production of three new models: a 2,700-horsepower freight locomotive, the FT, first produced in November 1939; a 1,000-horsepower switcher model, the NW2, first produced in January 1939; and a 2,000-horsepower passenger locomotive, the E3. The first E3 was EMC's demonstrator, completed in September 1938. A similar model, the E4, was first produced in October 1938, but only for Seaboard Air Line Railroad. The new E3, along with the near-identical E4 and E5 models, and the later E6 model, were all equipped with twin versions of EMC's new 1,000-horsepower Model 567 diesel engine, and the firm's new generators and traction motors. While the E3 demonstrators and the first E4s were built in late 1938, the first production E3s were completed for Union Pacific in March 1939.

Union Pacific received only two E3s. The lead unit was numbered as LA-5 and the booster unit was numbered as LA-6. The units were initially assigned to the City of Los Angeles, as indicated by their road numbers. When the City of San Francisco was wrecked at Harney, Nevada, in August 1939, the two E3s were reassigned to the temporary replacement train, along with the equipment from the older M-10004, and operated on that route until the E2-powered train was returned to service. In February 1941, the two units were renumbered to 5-M-1A and 5-M-1B, matching the new number series for non-City trains. (Previous published works show that the two unit numbers were 5-M-1A and 5-M-2B; recent research has found a painting and lettering drawing, and photos of the booster unit showing its number as 5-M-1B.)

With the return-to-service of the E2-powered City of San Francisco in August 1941, the E3s were placed into a general pool and used as needed on any of UP's Streamliner passenger trains. In 1946, the two units were renumbered to 951A and 952B, and again in 1948 to 991 and 992B. They were retired in 1956 and used as direct trade-in units for new E9s 901 and 904B.


UP continued to convert its passenger trains from steam to diesel power. In 1940, the road received six of EMC's latest offering, the E6. The E6 was itself a continuation of Electro-Motive's improving passenger locomotive design. It was very similar to the E3, E4, and E5 locomotives produced during 1938-1939; the E4s built solely for Seaboard Air Line (with standing nose doors); and the E5s (with fluted stainless-steel sides) built solely for Chicago, Burlington & Quincy. The six E6As built for UP, numbered as 7-M-1, 7-M-2, 8-M-1, 8-M-2, 9-M-1, and 9-M-2, were assigned as spare locomotives for the City trains, and as the first diesel units in the general passenger pool on the Eastern District, UP's Nebraska and Kansas Divisions. In 1946, these six units were renumbered to 953A-958A, and in 1948, they were renumbered again, to 992-997. As UP continued to modernize its passenger power fleet, these six E6s were traded to EMD in 1956 for new E9s.

In 1941, the service frequencies of the City of Los Angeles and the City of San Francisco each were doubled from five departures per month to 10 departures, using completely new equipment. Each additional train was equipped with 14 new cars, and a set of new A-B-B E6 locomotives from Electro-Motive Division (changed from Electro-Motive Corp. in January 1941). Each set was considered to be a 6,000-horsepower locomotive, made up of a 2,000-horsepower lead unit and two 2,000-horsepower booster units. The previous numbering system was continued, making the new power sets LA-4, LA-5, and LA-6 for the additional City of Los Angeles train, and SF-4, SF-5, and SF-6 for the added City of San Francisco train. These two power sets were possibly most notable as being the first diesel locomotives to wear UP's then-new standard colors of Armour Yellow and Harbor Mist Gray, with the gray replacing the previous Leaf Brown. These new Streamliner colors of yellow and gray were also applied to the new cars in these 1941 trains.

On July 13, 1943 the lead locomotive eastbound City of Los Angeles (E6A LA-4) was destroyed as the result of a head-on collision with a westbound freight train being pulled by UP 4-6-6-4 3825, as the passenger train departed the station at Carp, Nevada. As a result of the collision, the passenger locomotive rode up over the front of the steam locomotive, then fell to the side. Photos show that the cab of the passenger LA-4 locomotive was completely sheared off of the rest of the locomotive. Photos also show that the second unit in the passenger consist was E6B numbered as LA-5 with its unique red, white and blue "Buy War Bonds" paint scheme. Only the LA-5 lead unit derailed. The only injury was the fireman of the passenger train, who suffered a broken arm. (Story carried by both Associated Press and by United Press International newspapers, July 13, 1943; Beaver County News, July 15, 1943; photos in "Through The Rainbow Canyon" by Walter R. Averett)

The general renumbering of passenger motive power in 1946 changed the numbers of SF-4, SF-5, and SF-6 to 904A, 905B, and 906B, and LA-4, LA-5, and LA-6 were renumbered to 924A, 925B, and 926B. All were again renumbered in 1948 to jointly-owned 985J, 985BJ, 985CJ, 987J, 987BJ, and 987CJ. With the end of joint UP/C&NW/SP equipment ownership at the end of 1948, the 985J was taken by C&NW and renumbered 5004A as part of the final equalization. The remaining five units became UP 985B, 985C, 987, 987B and 987C. All were traded to EMD in 1956 on new E9s.

Joint-Owned Passenger Locomotives

As noted, the City of Portland, City of Los Angeles, and City of Denver Streamliner trains were operated over UP and Chicago & North Western tracks. The City of San Francisco Streamliner train was operated over UP, C&NW, and Southern Pacific tracks. For the first Streamliner trains (M-10001 and M-10002) the entire consist was wholly owned by Union Pacific and the other roads paid Union Pacific a use fee for each train consist. UP was charged by the other roads for expenses incurred while on their lines, and for use of their facilities, while on their respective trackage. The charges were based on complicated percentages and depreciation formulas, depending on the mileage that each train ran on each respective road.

With the arrival of the Pullman-built City of Denver (CD) sets, and EMC-built E2 City of San Francisco and City of Los Angeles (SF and LA) sets in 1937, and continuing with the E3s in 1939, the E6s in 1941, and the E7s in 1946, the three roads decided to actually share ownership of the equipment, with percentages of ownership based on the proportion of each road's route mileage to the total length of the run. Careful records were kept of all servicing and maintenance costs to facilitate equalization of expenses. The roads jointly owned the motive power on the trains, with fractions made up with spare engines and other components. When Union Pacific renumbered its entire diesel locomotive fleet in early 1948, some officials thought that the variety of locomotives used on passenger trains--some jointly operated and some exclusively UP--would make it difficult to keep accurate records for the purposes of equalization. To identify the joint-owned motive power, a "J" suffix was added to the road numbers.

Within nine months, the railroads realized that the separate accounting was unnecessarily cumbersome. This, along with other problems in the equalization procedures, lead to the cancellation of the joint ownership agreement on December 2, 1948, at which time the actual ownership of the equipment was redistributed according to a formula based on the percentage of mileage operated by each railroad. Chicago & North Western's share was three A units: E2A 984J, E6A 985J, E7A 988J; and two spare diesel engines. Southern Pacific's share was an A unit and two B units: E2A 983J and E7Bs 986BJ and 986CJ. Union Pacific took full ownership of all other remaining motive power in the pool.


Between November 1939 and September 1942, EMD continued to build new E6 units for American railroads (UP received its eight E6 cab units and six E6 booster units in August 1940, and in February and March 1941), with production ending because of World War II. As the war was coming to an end, EMD developed a successor model for the E6, which it named the E7. The two did not differ significantly, except in a shorter nose design, which the E7 (and all later E units) shared with the company's freight units, the FT and the upcoming F2 and F3. The first E7s were completed in February 1945.

Union Pacific's E7s were delivered in August 1946 to support the road's intent to boost Streamliner frequency to daily service. Before this, the City of Portland was running five times per month, and the City of Los Angeles and the City of San Francisco were each running 10 times per month. By tightening schedules and exchanging equipment assignments during 1946, the Portland train was changed to six times per month, and the Los Angeles and San Francisco trains were increased to three times per week (12 times per month).

Daily operation of the all-coach and the all-Pullman City trains between Chicago and Los Angeles-San Francisco-Portland, and UP's Challenger trains to both Los Angeles and San Francisco, were proposed as early as 1940. During mid-1944, with many believing that the end of World War II was near, UP again began to ponder the prospect of daily operation. In November 1944, one of UP's competitors, Great Northern, announced that it would begin running its Chicago-to-Seattle train on a daily schedule. In September 1945, the CB&Q-Denver & Rio Grande Western-Western Pacific combination announced that it intended to initiate a new daily lightweight train between Chicago and San Francisco. In June 1946, daily operation began on the City of St. Louis (a St. Louis-Denver-Los Angeles train operated jointly with the Wabash Railroad between St. Louis and Kansas City, Missouri.), and in February, May, and November 1947, daily operations began on the City of Portland, City of Los Angeles, and City of San Francisco, respectively.

The unique numbering system that UP used prior to mid-1946 included letter prefixes for units assigned to the City streamliner trains, such as SF for the City of San Francisco, LA for City of Los Angeles, and the unused CP for the City of Portland. By the time these E7 locomotives were ready to be delivered, UP had changed the numbering system, so that the E7s were the first units delivered wearing 900-series numbers (the Fairbanks-Morse Erie-built units were the first of any UP units to the receive 900-series numbers, in May 1946). E7A 907A and E7Bs 908B and 909B had been ordered as SF-7, SF-8, and SF-9; E7A 927A and E7Bs 928B and 929B had been ordered as LA-7, LA-8, and LA-9; and E7As 930A and 931A had been ordered as CP-1 and CP-2. These four cab units and four booster units all were delivered in August 1946 in their 900-series numbers after the passenger locomotive fleet was renumbered, which also took place in August 1946.

General pool units 959A and 960A had been ordered as 10-M-1A and 10-M-2A, and E7Bs 961B, 962B, and 963B had been ordered as 7-M-3B, 8-M-3B, and 9-M-3B. These two cab units and three booster units were also delivered in August 1946 in their 900-class numbers.

In mid-1947, EMD had completed an E7 demonstrator that operated with a four-car all-dome lightweight passenger train built by Pullman. The train (made up of the first dome cars) known as the "Train of Tomorrow," toured the United States, visiting 86 cities. Afterward, EMD sold the train to UP in March 1950. The E7 locomotive, EMD number 765, became UP 988. The entire train was put into service as a connection between Seattle, Washington, and Portland, Oregon, connecting with the City of Portland streamliner between Portland and Chicago.

As noted, UP E7A 988J was sold to C&NW in 1948 when the joint ownership agreement was ended. Likewise, UP E7Bs 986BJ and 986CJ were sold in 1948 to Southern Pacific. UP traded the remaining six E7As and five E7Bs to EMD in 1961-1963 on new E9 units.

Yard Switch Service and EMD NW2s

Union Pacific's newest 0-6-0 steam switchers were built in 1920 and 1921. By the late 1930s, UP was also using 2-8-0s and small-drivered 2-8-2s in switching service. While this service had not been demanding, UP by 1939 was ready to replace these engines with newer designs. Like several other roads, UP had been watching the development of small diesel locomotives closely, and in that year, accepted EMC's offer to demonstrate examples of its two newest switcher designs. In October 1939, 600-horsepower SW1 demonstrator 911, and 1,000-horspeower NW2 demonstrator 889, arrived on UP property in Omaha. The two units were used extensively by UP in both its Omaha, Nebraska, and Council Bluffs, Iowa, terminals. At the end of the six-month demonstration period, the railroad found the SW1 to be too light and underpowered for UP's purposes, and returned it to EMC in March 1940. UP, however, found the other locomotive to be satisfactory and purchased it, renumbering it to UP 1000. The following month, UP placed an order with the builder to deliver 14 additional NW2s. Still more NW2s were delivered prior to the imposition of wartime restrictions--10 units in early 1941 (UP 1015-1024), two units in late 1941 (UP 1025, 1026), and nine units in 1942 (UP 1027-1035).

In August 1941, UP had ordered 25 more NW2s from EMD (changed from EMC earlier that year). Two were delivered as UP 1025 and 1026 in October. At the same time, with American industry furnishing so much assistance to the Allies in World War II prior to the U.S. actually entering the war, the federal government placed restrictions on UP's plan to acquire additional diesel switchers. By the following April, UP had negotiated with the War Production Board to acquire nine more (of the original 25-unit order), which were delivered from May to July 1942. The remaining 14 units were canceled on July 14, 1942.

UP still needed additional yard switchers, and acquired 19 American Locomotive Co. S-2s, numbers 1036-1054, a year later, beginning in September 1943. These units were later renumbered to UP 1100-1118. The production of EMD switchers remained blocked for the remainder of the war, but UP still needed additional diesel switchers. To fill this need, the road acquired 33 more Alco S-2s (UP 1119-1151), six Baldwin VO-1000s (UP 1055-1060, renumbered to UP 1200-1205), and a single Fairbanks-Morse H10-44 (UP 1300).

(Read more about all of Union Pacific's NW2 Yard Switching locomotives)

Alco, Baldwin, and Fairbanks-Morse Switchers

After Union Pacific made the decision to dieselize its yard switching fleet in 1940, two difficulties prevented the full implementation of this strategy. Operations officials submitted a budget plan to upper management that would add 15 to 25 diesel switchers each year, with each diesel switch unit replacing steam switchers on a one-for-one basis. The first difficulty was wartime restrictions. Modern switchers were needed due to increasing traffic stemming from supplying the war in Europe, and that same war would soon directly involve the United States. UP selected the 1,000-horsepower NW2 unit from EMD as its diesel switcher of choice. Unfortunately for Union Pacific, the NW2 model was also popular with many other railroads. Just as UP had received its first 25 units, and had ordered another 25 units, wartime restrictions forced the cancellation of 14 of those 25 units, and delayed the final delivery of the remaining 11 units.

UP still needed more diesel switchers, so the federal government allowed the road to order from the other builders, Alco and Baldwin. In 1943 and 1944, the railroad accepted 19 Alco 1,000-horsepower S-2 units and six Baldwin 1,000-horsepower VO-1000 units, all numbered in consecutive number series following the initial NW2s. In early 1945, with the war ending soon, UP was allowed to order 10 more Alco units and 15 more EMD units. The road also acquired a single Fairbanks-Morse 1,000-horsepower unit, an H10-44 numbered UP 1300, to explore the capabilities of the builder's adaptation of its successful opposed-piston submarine diesel engine that had proven itself so well during the war. But the railroad needed still more diesel switchers, a need that was projected to be even greater with the end of the war.

This post-war need for many more diesel switchers brought the second difficulty into focus--the inability of EMD to deliver all the diesel switchers needed by all of America's railroads. EMD had proven its design to the satisfaction of the railroads, but could not build them fast enough. Diesel switchers had shown that they were capable during the war, and many railroads wanted more of them as soon as possible. In early 1945, UP wanted 25 more switchers, but to get them in a timely fashion, the road was forced to split the order: 10 to Alco and 15 to EMD. Twenty-five more Alco units were ordered in mid-1945. Because Alco was not working at the full capacity that EMD was, the Alco units (a total of 35 of them) were delivered in mid- to late 1945, while the 15 EMD units came much later, in mid-1946. EMD was soon able to expand its production, and during 1947 and 1948, it delivered 45 more NW2s to UP. To fill out its need for still more diesel switchers, UP took delivery on five more 1,000-horsepower units from Baldwin, and four more FM H10-44s, all in 1948.

Within two years, EMD had improved its switcher design, using SW7 to designate its then-current 1,200-horsepower model. In that same year, 1950, UP acquired 25 such units, numbering them 1800-1824. In 1953, 42 of EMD's newest, the 1,200-horsepower SW9, came to the road as UP 1825-1866. By 1954, still more switchers were needed. UP asked EMD for more SW9s, but questions surfaced at the top levels of UP's management, following placement of a large order to EMD for GP9 freight road switchers, over the wisdom of depending so heavily on a single builder to dieselize the railroad's operations.

Both the Baldwin and Alco switcher designs had proven to be costly to maintain, and the Alco design for road locomotives (sets of FA/FB cab/booster units furnished to UP in 1947) had proven to be so troublesome that UP hesitated asking for anything other than EMD. Bowing to pressure from its board of directors, the railroad ordered 35 units of Alco's latest 1,000-horsepower model, the S-4, which were delivered from mid-1955 to early 1956. These proved to be UP's last new diesel switchers, due mostly to the low horsepower and lack of flexibility of all purpose-built diesel switchers. UP soon learned that lower-horsepower road-switcher locomotives easily filled the switching role, and, unlike a switcher, could also be used in regular road service.

GE 44-Ton Switching Locomotive

A General Electric light center-cab switching unit, UP 1399, was delivered to UP in March 1947 as the first unit of an intended three-unit order. The model had been designed and built to support single-man operation, after the operating unions had allowed that a unit weighing less than 88,000 pounds (44 tons) could be operated by only one crew member. After testing, the unit was found to be both too light and underpowered, leading UP to cancel the other two units of the order. The unit was first assigned to yard switching duties in the Omaha area, then as shop switcher for Omaha Shops; then in late 1956, it was transferred to the Roadway Department and renumbered to 03999. It was used at the System Roadway Equipment Shop at Pocatello, Idaho, until late 1972. Along the way, it had been renumbered once again, to 903999, in December 1959 during a general renumbering of all roadway equipment, which added the digit 9 as the first digit and additional digits to the end of the number to bring it into the 900000 series.

First Freight Units

After its successful introduction in 1939, the Electro-Motive FT cab-unit locomotive was viewed by many industry observers as the clear choice by which railroads would displace steam power from heavy mainline freight service. Although UP had purchased early examples of diesel passenger power from Electro-Motive for its Streamliner fleet, when the builder offered to sell UP its FT locomotive model (at 5,400 horsepower), UP responded by saying that as soon as EMD could build a diesel locomotive that could match the performance of its 4000-class 4-8-8-4 Big Boy locomotives (at approximately 6,300 horsepower) on the Wasatch grade in Utah, then UP would be interested.

Undaunted by this rebuff, EMD went on to sell the FT model to every one of UP's competitors--Santa Fe, Great Northern, Northern Pacific, the end-to-end Rio Grande and Western Pacific roads, and Rock Island, which handled a share of UP's Chicago-Omaha business but also competed with the road for California traffic via its Tucumcari., N.M., gateway with SP. In August 1945, UP President William "Bull" Jeffers believed the FT to be barely adequate for its time, fearing that its technology would soon be obviated by developments in gas-turbine or atomic-power technology. But having said what he did in August 1945, within three months, as a demonstration of his interest in the changing motive power picture, he allowed EMD to test its FT replacement, the F3.

As a comparative side note to UP's staying with steam motive power, railroad historian Dan Cupper points out that Jeffers' cautious stance in the west was similar to that of the conservative Pennsylvania Railroad in the east. PRR, like UP, believed that the future lay with bigger and better steam engines, embarking on a binge of building complex, custom-designed high-horsepower steamers of 6-4-4-6, 4-4-4-4, 4-4-6-4, and 6-8-6 (steam turbine) designs. Although these were not nearly as successful as UP's modern steamers, Pennsylvania remained unconvinced that the diesel was capable of being anything more than a yard switcher. As with UP's Jeffers, EMD was unsuccessful at enticing PRR to nibble at the FT, and instead sold the model to every one of Pennsylvania's trunk-line competitors--NYC, Baltimore & Ohio, and Erie Railroad--and some of its other rivals as well, such as Reading.

Earlier, however, Jeffers had been impressed with EMC's efforts. In an October 1938 letter, he wrote that EMC was making "amazing progress in further developing and improving diesel power," identifying the main competition for diesel road locomotives as the steam turbine then under construction at GE, and the then-new 800-class 4-8-4 steam locomotives that Alco had just delivered to UP. He went on to say that UP's 2,000-horsepower diesel passenger model (the E3) represented "an outstanding job," with the price per horsepower, at $85, comparing very favorably with the previous rate of $100 or more. Jeffers' eventual disdain for the FT still lay in the future; while the locomotive was on the drawing board, he was willing to compliment it, saying that it would give the steam builders something to compete with.

Another factor that kept UP from dieselizing earlier was the cost of diesel fuel, which almost tripled just before the war, and was also rising rapidly at war's end. More diesel units meant more diesel fuel, but more steam locomotives could use coal, a resource that the railroad already owned in abundance with its coal mines in Wyoming.

During the final years of World War II, UP was looking seriously at dieselizing its South-Central District, due to that desert region's expensive water and fuel oil facilities. The railroad wanted to dieselize the line with a fleet of double-unit, 6,000-horsepower locomotives. Like most of the nation's other railroads, UP also was making more general plans to upgrade its motive power fleet by replacing the hundreds of steam locomotives that had served so well during the war. At the end of the war, the South-Central District was still all-steam, except for the City of Los Angeles streamliner train that operated 10 times per month.

Both Baldwin and Fairbanks-Morse responded to the projected 6,000-horsepower design specification. Baldwin floated a proposal for two of its very long DR12-8-1500/2 locomotives, nicknamed "Centipedes" for their many wheels (each cab unit of a two-unit set used a 2-D+D-2 wheel arrangement, meaning eight unpowered axles and 16 drive wheels per unit). F-M responded with its proposed design that used three units, each with a 2,000-horsepower version of its proven opposed-piston engine. Due to a lack of manufacturing facilities, the FM locomotives would have to be built under contract at GE's Erie, Pa., factory.

During 1945, as the war was ending, railroads had little from which to choose in the way of a road freight locomotive design, a fact soon discovered by UP and the other roads. EMD was still offering its FT locomotive, and the other builders were frantically gearing up to fill the perceived post-war demand for new locomotives.

The other builders were also settling on the 6,000-horsepower road locomotive, like EMD with A-B-B sets of its then-new E7, first offered in February 1945, and A-B-B-A sets of its then-new F3, first offered in July 1945. All the builders were soon offering the 6,000 horsepower locomotive either as a three-unit set with A1A trucks for passenger service (12 powered axles), or as a four-unit set with B-B trucks for freight service (16 powered axles).

For its freight locomotive, Alco would soon offer its own four-axle 1,500-horsepower carbody unit, later known as the FA/FB, with the first unit being produced in January 1946. Baldwin first offered its own 1,500-horsepower carbody unit in September 1945. For passenger units, the first Alco postwar passenger units, the six-axle 2,000-horsepower PA/PB design, were first produced in June 1946. Baldwin was offering its own six-axle 2,000-horsepower passenger unit, with production of two demonstrators completed in January 1945. UP was still unimpressed, however. A big part of the reason was that the road had just received the last 35 of its 175 modern steam locomotives less than a year earlier, and was satisfied with their performance.

While the diesel builders wanted to produce locomotives that could be connected into multiple-unit consists, UP was looking for single- or double-unit locomotives that could directly replace steam locomotives. UP had learned that the maintenance costs per unit (either steam or diesel) remained basically the same, regardless of the unit's power, and was therefore looking for diesel locomotives that packed more horsepower.

Into this atmosphere came both Baldwin and Fairbanks-Morse. The demonstration tour of Baldwin's number 2000, a 2,000-horsepower A1A-A1A unit, began on the Reading Railroad in January 1945, and ended with the unit's sale to National of Mexico in August of that year. The tour included a trip over Denver & Rio Grande Western between Denver and Salt Lake City, returning to Denver in April. Notably, the unit did not tour on UP. However, Baldwin's potential must have impressed UP. In January 1945, UP President Jeffers approached Baldwin about building a 6,000-horsepower combination freight and passenger locomotive for service between Salt Lake City and Los Angeles. Within a year, UP ordered Baldwin's massive locomotive (later known as "Centipedes"), made up of two 3,000-horsepower units. But prior to the Baldwin order, the railroad first ordered an example of Fairbanks-Morse's 6,000-horsepower entry.

F-M Erie-Builts

Union Pacific AFE (Authority For Expenditure) 282, dated August 31, 1945, says this: "Purchase one 6,000 horsepower combination freight and passenger locomotive (three units) from Fairbanks-Morse. Price $600,000. For Salt Lake City to Los Angeles service."

Because FM did not have the production capacity at its Beloit, Wisconsin, plant, the units were built by General Electric under contract at GE's Erie, Pennsylvania, factory, hence the "Erie-built" nickname. The order was accepted as F-M order LD6, the sixth locomotive to be built by this new builder. F-M's fourth locomotive order (LD4) was a switcher for Union Pacific, completed in May 1945 as UP D.S.1300 (the D.S. prefix meaning Diesel Switch).

October 13, 1945
"The Union Pacific will receive from Fairbanks, Morse & Co., on November 1 a three-unit, 6,000-hp. Diesel-electric locomotive, which has been designed for a maximum operation of 65 m.p.h. This locomotive will be tested on a run from south of Salt Lake City, Utah, to Los Angeles, Cal., in freight hauling and possibly in passenger service. The Union Pacific will also receive a four-unit, 6,000-hp. Diesel-electric locomotive from the Electro-Motive division of the General Motors Corporation, which is to be tested between Green River, Wyo., and Ogden, Utah, under exact loads and conditions to determine comparison of performance of this unit with the Union Pacific's "Big Boys," or 4000 class, 4-8-8-4 type, locomotives. Later tests of the new locomotive will also be conducted between Salt Lake City and Los Angeles." (Railway Age, October 13, 1945, page 622)

This set of two Erie-built cab units and a single booster unit was delivered in December 1945 as UP 50-M, with the three units (A-B-A) sub-numbered as 50-M-1A, 50-M-3B, and 50-M-2A. The M suffix stood for Motor, and fell in line with the road's other diesel power, with numbers such as 5-M for its E3s, and 7-M to 9-M for its E6s.

April 19, 1946
"The first of the new Union Pacific Diesel locomotives in service on the Los Angeles division made a test run over Cajon Pass Friday (April 19, 1946) pulling 850 tons of freight with no helper. The bright yellow four-unit job carries the number M-50." (San Bernardino County Sun, April 21, 1946)

June 3, 1946
Union Pacific announced the formal purchase of a 6000 HP three-unit locomotive made by Fairbanks-Morse. The locomotive had been under test in passenger service between Chicago and Los Angeles for the past five months. The locomotive had a maximum speed of 102 miles per hour. (Provo Daily Herald, June 3, 1946)

UP's Erie-built units were the first of the model to be completed. A later note attached to the AFE states that the units were geared too high for freight service, but too low for passenger service, and that they were converted to 104 mph gearing for passenger service. The purchase was approved based on satisfactory performance in high-speed passenger service. These units were delivered in late December 1945, and converted to passenger service in May 1946. FM eventually built a total of 54 Erie-built locomotives for railroads in the U.S., including eight cab units and five booster units for UP.

(Read more about UP's Erie-built locomotives)

Baldwin Centipedes

In October 1945, two months after the Erie-builts were ordered, UP placed an order for Baldwin Centipedes. AFE 314, dated October 24, 1945, reads, "Purchase one 6,000 horsepower combination passenger and freight locomotive (two units) for operation between Salt Lake City, Utah, and Los Angeles, California. From Baldwin Locomotive Works. Total cost of $600,000. Expected delivery during third quarter 1946."

These two units were to be UP's diesel answer to their highly successful Big Boy 4-8-8-4 steam locomotives, and were to enter service on the LA&SL between Los Angeles and Salt Lake City. The Centipedes were also 4-8-8-4. Using the AAR designation, they were 2-D+D-2.

The following comes from a small pamphlet published in 1946, called "Union Pacific Railroad, A Brief History." It is the only published acknowledgment that UP had ordered the Baldwin Centipede locomotives.

The railroad in mid-1946 purchased a 6,000 horsepower, three unit diesel locomotive from Fairbanks-Morse for passenger train use, and ordered a second 6,000 horsepower freight diesel, in two units, from the Baldwin Locomotive Works; both locomotives being of new and improved design in the diesel field.

The order was canceled in April 1947 after a promised August 1946 delivery date was changed to August 1947. In late March 1947 a UP representative who visited the Baldwin factory near Philadelphia found that no material had been marked for the locomotive, or that any "lay-down plans" even existed. There was an unconfirmed report on the LocoNotes email discussion group in February 2002 that the Baldwin order was canceled following a meeting of railroad presidents where the Seaboard Air Line president told the Union Pacific president that the SAL units "had terrible oil leaks." This was likely not the sole reason that the order was canceled, but it may have contributed to the decision.

The two units were completed a year later, in March 1948, as Baldwin demonstrators 6000 and 6001, and were used in a limited demonstration tour that did not generate any additional sales. Both units were quietly scrapped by Baldwin after furnishing parts for wreck repairs to similar Pennsylvania Railroad and National of Mexico units.

The first example of what Baldwin called its model DR12-8-1500/2, and known to railfans as "Centipedes," was completed as Seaboard Air Line 4500 in December 1945. Thirteen more were completed for SAL between March 1947 and January 1948. Each locomotive generated 3,000 horsepower, rode on eight driving axles, was powered by two diesel engines, and weighed a total of 595,000 pounds. NdeM in Mexico received 14 units between April 1947 and July 1948, and Pennsylvania Railroad received 24 between April 1947 and February 1948. The entire fleet totaled 54 units, all completed between December 1945 and July 1948.

Until recently, locomotive and Union Pacific historians have always been under the assumption that the intended road numbers were UP 998 and 999, as stated by Baldwin historian John Kirkland in his 1994 book about the history of Baldwin diesel locomotives. (John F. Kirkland, The Diesel Builders, Volume 3, Baldwin Locomotive Works, Interurban Press, 1994, page 137)

The problem is that those two road numbers (UP 998 and 999) would have been way out of sequence for UP's numbering plan at that time. The 900-series numbers were first used on the renumbered FM Erie-builts in May 1946, as UP 981A, 982A, and 983B. If the two Centipedes were indeed to be numbered as UP 998 and 999 (with their intended August 1947 delivery), they would have been UP 998A and 999A, since the A and B suffix scheme was not dropped until early 1948. In mid-1946 the entire diesel passenger fleet was renumbered. The numbers assigned were UP 901A to 909B, 921A to 931A, and 951A to 963B (including A units and B units, and all the E7s delivered in August 1946).

After the Centipede order was canceled in April 1947, additional passenger units were delivered in September 1947 in the form of the F3As and F3Bs, delivered as UP 964A to 978B. The numbers in question, UP 998 and 999, were used in September 1947 when UP's first Alco passenger booster units, later known as PB-1s, were delivered as UP 998B and 999B, in sequence with the first four Alco passenger cab units, later known as PA-1s, UP 994A-997A.

Recent research has found a reference to a drawing for the painting, lettering and numbering of these planned Baldwin Centipede units. It is UP drawing 357-ST-4553, dated March 4, 1947 (about a month before the order was canceled). It shows the planned road numbers as being UP 1600A and 1601A. Unfortunately, the drawing itself isn't available at this time, but it is shown in an index of thousands of other UP drawings of the mid 1930s through the late 1970s.

These two road numbers (UP 1600A and 1601A) for the two Centipedes fall right in line with UP's numbering scheme at the time: 1000s for EMD switchers, 1100s for Alco switchers (and later road units), 1200s for Baldwin switchers (and later road units), 1300s for F-M switchers (and later road units), 1400s for EMD road freight units, and 1500s for Alco road freight units. The A-B-A set of F-M Erie-builts had just recently been renumbered to the 900 series, along with all of the road's EMC and EMD passenger units. In 1948, after the Centipedes were canceled, the Alco road freight units were renumbered to the 1600s to allow for the increasing numbers of EMD road freight units to occupy the 1500 series.

(Photo of a Seaboard Air Line unit on the cover of Railway Age magazine -- a UP version of the locomotive would have looked similar)

The First EMD Cab Units

Union Pacific continued to embrace modern steam locomotives right through 1944: 4-6-6-4 Challengers delivered in 1936-37 and 1942-1944; 4-8-4- Northerns delivered in 1937, 1939, and 1944; and 4-8-8-4 Big Boys delivered in 1941 and 1944. This was why when the EMD salesman came calling sometime in 1942-1943, UP's President Jeffers told him, "When you can equal the Big Boy up there," he said, pointing to the picture of a steam locomotive on the wall of his office, "come around and we'll talk business."

This was typical Jeffers, but because he had a profitable railroad to run, he was always looking to cut costs and continued to look at the new diesel technology. By mid 1945, UP's management was aware of the increase in traffic that was expected with the end of World War II, and saw that their fleet of modern steam locomotives may not be able to handle the increase. Also, the board of directors was putting pressure for UP management to become a modern railroad, with new diesel locomotives.

In July 1945, EMD completed a set of demonstrator locomotives with design changes meant to replace its earlier FT model. This new model was known as F3 and included all new technology for both the diesel engine, and the electrical gear. This demonstrator set was sent on the road, including a tour on UP. A newly discovered railfan report by Bill Garner in November 1945 (published in the December 1945 issue of Pacific Railroad Society's Wheel Clicks) reported that, "The Union Pacific has been trying out a big General Motors diesel on the hill. In fact, it is being tried out between Los Angeles and Salt Lake City. After these trials it is to be tried out east from Ogden and compared with the 'Big Boy' mallets."

The locomotive that was tested was likely EMD's number 291, a set of two F3 cab units and two F3 booster units (A-B-B-A), and the report falls right in line with UP's interest in the Fairbanks-Morse and Baldwin cab units, as covered earlier. The tour must have impressed UP's management, because a year later, the board of directors approved the concept of buying diesel locomotives in quantity.

Evidence that the locomotives being tested were EMD F3 291 set comes from a bit of research: On page 48 of the July 1950 EMD Product Reference data, it shows that the EMD 291 A-B-A set was built in July 1945, so this was likely what was seen in November 1945. Of course, it was entirely possible that EMD was loaned a set of units from another railroad for this test, since they did that several other times when they found that their demonstrators were spread a little thin. I'd like to see a photo of the F3 demo set on Cajon in November 1945. many may assume that it would have been an AT&SF test, but apparently it was a UP test.

The timeline for UP's diesel locomotive purchases matches this November 1945 test. A year later, In December 1946, UP's board approved the order for 162 units at a cost of $22 million. On January 5, 1947, AFEs (Authority For Expenditure) 5 and 6 were approved for the purchase which included a total of 47 F3 cab units and 45 F3 booster units. Although the quantities were later reduced, the initial orders were themselves significant.

It took a complete change in top management at Union Pacific to prompt the road to become serious about modernizing its motive power, and begin buying large numbers of diesel locomotives. George F. Ashby replaced Jeffers as UP president upon Jeffers' mandatory retirement in January 1946 at age 70. Ashby was almost the complete opposite of Jeffers in his approach to management, and he proceeded to do everything Jeffers would not have done, including ordering a large fleet of EMD F3s and Alco FA/FBs in 1946-1947. Having an extensive accounting background, rather than an extensive operating background, which Jeffers had, Ashby took the attitude that the builders were offering a good product, and that UP should take advantage of these new standardized locomotives. By contrast, Jeffers' view (a holdover from the steam days) was that the builders should build locomotives to Union Pacific's specifications, or at least to UP's unique operating environment. It was a question of who would spend the dollars in engineering and developing the much-needed replacement motive power. By buying designs already engineered by the builders, UP could spend its own money on improving its own right-of-way and facilities.

Another factor to be considered in whether Union Pacific should dieselize its motive power fleet was its image as a modern road to both current and potential investors. Specific studies and hard data aside, by the end of World War II, the use of diesel locomotives by any particular road was seen as evidence of that road being thoroughly modern and up-to-date. So, even if UP's fleet of 175 modern (built after 1935) steam locomotives was performing with costs and results comparable to the new diesel locomotives of other railroads, UP's management wanted to be viewed by the Wall Street investment community as modern and up-to-date.

In mid-December 1946, less than a year after Jeffers' retirement, the road placed an order for 133 units, at a cost of $20.4 million, with delivery to take place during the third quarter of 1947. The order covered units from Alco and EMD. All of this power was intended to allow the complete dieselization of the railroad west of Green River, Wyoming, or at least the South-Central District, from Salt Lake City to Los Angeles.

December 28, 1946
The following comes from the December 28, 1946 issue of Railway Age magazine:

U. P. Orders 35 More Diesel Locomotives, Total 64 -- Union Pacific orders for 35 road Diesel-electric locomotives; 7 passenger and 28 freight units -- announced last week by G. F. Ashby, president, bringing that road's recent Diesel-electric locomotive orders to a total of 64 units, costing $22,000,000. Previous orders for 29 Diesel-electric switchers, at an estimated cost of $3,000,000, were reported in the Railway Age of December 21.

Comprising the largest Diesel locomotive order in railroad history, the 64 new units will afford complete Dieselization of the U. P. south of Salt Lake City, Utah, by the fall of 1947, Mr. Ashby stated. He said that, upon delivery of the locomotives, the road will have a total of 178 single Diesel units for freight and passenger traffic and 141 Diesel switch engines.

When all of this equipment is received, the Union Pacific will have -- including the 45 units now in use on passenger trains and the 112 Diesel switchers now in service -- a total of 421,500 hp. in Diesel-electric locomotives, Mr. Ashby said. "There will be 112,500 hp. in passenger service, 168,000 hp. in freight service and 141,000 hp. for switching activities."

The number of locomotives, type, manufacturer and expected 1947 date of delivery of the 35 additional units are as follows: Two 6,000-hp. passenger, of three 2,000-hp. units each, American Locomotive Company, with delivery in May; five 4,500-hp. passenger, of three 1,500-hp. units each, Electro-Motive Division of General Motors Corporation, with June delivery; 10 6,000-hp. freight, of four 1,500-hp. units each, Alco, April delivery; and 18 6,000-hp. freight, of four 1,500-hp. units each, Electro-Motive, September delivery.

Early Non-Streamliner Passenger Units

Beginning in 1947, UP began replacing all steam power on passenger trains on the South-Central District (the former Los Angeles & Salt Lake Railroad, between Salt Lake City, Utah, and Los Angeles, California.), especially non-Streamliner trains, such as the Pony Express, the Los Angeles Limited, and the Utahn. The first units to be used were the A-B-A set of Fairbanks-Morse Erie-built units. These had been converted to passenger units in May 1946, and were the first units to carry the road's then-new passenger-designation 900-series numbers, as 981A, 982A and 983B. To begin this conversion from steam to diesel, UP in September 1947 received its first passenger F3 units from EMD -- five cab units, numbered 964A-968A, and 10 booster units, numbered 969B-978B. These were operated in A-B-B sets that each made a 4,500-horsepower locomotive, to be used on the trains that usually ran with fewer cars.

Also in September 1947, for the heavier passenger trains, UP received its first Alco 2,000-horsepower PA/PB units, numbered 994A-997A and 998B and 999B. These ran in A-B-A sets that added together to make a 6,000-horsepower locomotive. In November, the road's first additional Fairbanks-Morse Erie units arrived, numbered as 984A, 985A, 986B, and 987B. Because of their similar electrical gear (General Electric), the Alco and FM units were used together on many occasions.

In 1948 and 1949, UP took delivery of additional units from all three builders. Union Pacific eventually operated a fleet of 54 units for its non-Streamliner passenger trains, including 11 F3 passenger cab units, 16 F3 passenger booster units, eight Alco PA cab units, six Alco PB booster units, eight FM Erie cab units, and five FM booster units. These units remained in passenger service, usually on the South-Central District, and at times operating with the 12 1400-series F3 booster units also equipped for passenger service, until the arrival of a large fleet of E8 and E9 locomotives in 1953-1956. The arrival of these newer locomotives allowed UP to convert the earlier units to freight service. In the fall of 1954, the Alco units were moved from the South-Central District to the Eastern District.

In the general renumbering of early 1948, the Alco units were renumbered from the 900 series to the 600 series; the FM units were renumbered to the 700 series; and the EMD units were renumbered to the low-900 series.

Atlantic City, June 1947

In a move to show that the railroads were modern and up-to-date, two divisions (Mechanical, and Purchasing and Stores) of the American Association of Railroads held their annual convention on June 23-28, 1947 at Atlantic City, New Jersey. At the same time, the Railway Supply Manufacturers Association held its annual trade show. Equipment later owned by Union Pacific was among the 260 manufacturer's displays, with some equipment being placed on a special half mile of track laid for the purpose adjacent to the Atlantic City Convention Hall.

The displays included locomotives from Fairbanks-Morse, built as demonstrators. These included H20-44 number FM-2000, which became UP 1366 immediately after the convention. Along with the H20-44, Fairbanks-Morse had as part of its display two cab units of its streamlined locomotive which later became known as Erie-Builts. UP 984A and 985A were completed in June, and were shipped right away to Atlantic City. After the convention, the two Erie-builts went on a demonstration tour on B&O, including runs between Philadelphia and Washington D.C. The tour of B&O lasted for about 30 days, after which the two units were returned to the F-M factory at Beloit to be reconditioned, and were delivered to Union Pacific in August 1947.

Also at the Atlantic City convention was General Motors' Train of Tomorrow, which had only been turned out of the EMD La Grange factory on June 2nd. The train was first displayed at Chicago, then Detroit, then Toledo and Pittsburgh, then on to the Washington D. C. area at Silver Springs, Maryland, where several rounds of special luncheons were provided for government and industry leaders. Then it was on to Atlantic City on June 22nd, in time for the AAR convention. The GM Train of Tomorrow continued its national tour for another two years, until October 1949, and was finally sold to UP in April 1950.

Full Dieselization Begins

In 1947, Union Pacific began the dieselization of its freight locomotive fleet. That year, the road acquired a total of 129 passenger, freight, and switch diesel locomotives, from all four builders (apparently, four units of the original 133-unit order were not delivered). Included were the company's first road switchers: UP 1190, an Alco RSC-2, and UP 1191, an Alco RS-2. Both were delivered in February 1947.

Union Pacific's first diesel-powered freight train to operate between Salt Lake City and Los Angeles, departed Salt lake City on the morning of Tuesday June 3, 1947. A second diesel-powered freight was scheduled to depart Salt Lake City in the afternoon of the same day. There were already 14 diesel switching locomotives assigned to Salt Lake City and vicinity, and UP had ordered 13 additional switching locomotives for the same service. (Deseret News, June 3, 1947, with photo of UP 1401A)

The diesel program continued into 1948, when UP bought 233 more locomotives, again for all types of service and from all four builders. Included were additional road switchers. UP 1250, a DRS-6-4-15 that had been a former Baldwin demonstrator, came in January 1948. Alco supplied three RS-2s and 10 RSC-2s from February to April 1948.

After initially purchasing a large, new fleet of diesels in 1947 and 1948, Union Pacific held back on further mass acquisitions over the next five years, buying only 19 units in 1949 and only 13 units in 1950. During 1951, the railroad bought 65 locomotives, including a group of F7 units, successor to the F3 model. UP purchased only 18 diesels in 1952, many of them actually being units that were rebuilt from wrecked locomotives. The road continued to assign its diesel fleet for maximum savings, and re-assign its steam fleet, to get as much mileage and return on its investment in the large fleet of modern steam locomotives that had been purchased just 10 years before.

Traffic that had been swelled by postwar industrial growth and the war in Korea again forced UP to purchase additional diesel locomotives to modernize its fleet. In 1953, UP bought 121 units, including SD7s, GP7s, SW9s, E8s, and gas-turbines. The expansion of the diesel roster continued into 1954, when the road bought 274 diesels, including GP9s, E9s, and still more gas-turbines. In 1955 and 1956, the modernization of the passenger and switcher fleets was the emphasis, as the railroad bought EMD E9s and Alco S-4s--a total of 65 locomotives in 1955 and 23 in 1956. During the following year, 1957, UP purchased 100 GP9s (50 A-units and 50 B-units), the delivery of which in effect brought an end to the use of steam power on Union Pacific.

Alco RSC-2 and RS-2 Road Switchers

In one of the earliest uses of diesel locomotives in freight service on UP, Alco furnished an RSC-2-model six-axle (four of them powered), 1,500-horsepower demonstrator road switcher in March 1947 to show the railroad what a road switcher could do. Alco numbered the unit 1190 and painted it in UP's yellow and gray, but without UP lettering. The railroad put the unit to work on its Laramie, North Park & Western subsidiary, operating out of Laramie, Wyoming. (later this line became known as the 111-mile Coalmont Branch). On April 29, 1947, UP management approved an AFE to purchase this locomotive, although the sale was not made final until mid-March 1948. The request to purchase the unit came after the unit had tested on both the LNP&W, and on branches in Washington, during which it had shown itself capable of handling 450 tons (about nine cars) more than the then-currently assigned 2-8-2 Mikado steam locomotives. And it would allow the abandonment of LNP&W coaling facilities, plus at least four LNP&W steam locomotives (seven LNP&W 2-8-2s were retired in May and June 1947).

After the success of the 60-day RSC-2 demonstration, and the purchase of that unit, UP bought 10 more RSC-2s and five of their four-axle brothers, the mechanically identical RS-2. This was authorized in the January 1948 AFE that approved the purchase of 188 additional diesel locomotives. The RSC-2s were used on the branches with very light rail and bridges, including the Cache Valley Branch in Utah, while the RS-2s were to be used on the newer branches with heavier rail, and as heavy switchers.

With the arrival of 10 more units (UP 1180-1189) from February to April 1948, it was an Alco RSC-2, known then simply as a "six-axle Alco," that bumped UP's Shay steam locomotives from their assigned home terminal at Tintic Junction in central Utah (Shays 59 and 61 were retired in February 1949 and September 1948, respectively).

In answer to a question in September 2001, Don Strack wrote:

The Alcos were used in Utah on the Eureka, Mammoth, and Silver City branches (sometimes known collectively known as the Tintic Subdivision) and on the Cache Valley Branch. Current research suggests that they left Utah with the arrival of the GP7s and GP9s in about 1955. They were delivered as UP D.S. 1180-1189, and were renumbered to UP 1280-1289 in October 1955. The D.S. prefix was likely removed in late 1953. With their reassignment to the Eastern District in 1955, the units received the later cross-wise exhaust stack that denoted a water-cooled turbocharger. They may have also received at the same time, most of the branchline add-ons that Gary Binder mentioned.

To directly answer Scott's question, the RSC-2s were used in Utah in branchline service from 1948 to 1955, and they operated with road numbers of 1180-1189, with regular-height length-wise exhaust stacks. Although there are few photos, the Cache Valley unit(s) would have been sent to Ogden for maintenance and would be seen side by each with late steam, but not used on the same trains, or even on the same division. The Tintic unit(s) would have been sent to Lynndyl (or maybe Provo) for maintenance, but their would have been few late steam, except at Salt Lake City, where an occasional OSL Challenger operated until about 1956. (Don Strack, email to UP Modelers Yahoo group, September 17, 2001)

EMD F3s and F7s

Union Pacific selected the EMD F3 and the Alco FA/FB locomotive with which to dieselize its freight operations between Salt Lake City and Los Angeles. Each was the most recent offering from its respective builder, each generated 1,500 horsepower, and UP purchased each in matched A-B-B-A sets of cab units and booster units. In 1947, UP received five A-B-B-A locomotive sets in the 1400 class from EMD, and eight A-B-B-A locomotive sets in the 1500 class from Alco. These EMD units became the first of a fleet of 89 cab units and 90 booster units of the F3 model, with additional F7 units coming in later years.

The first units of the first order of F3s arrived on UP in May 1947, numbered 1400A-1403A for the cab units, and 1442B-1445B for the booster units. They were delivered in A-B-B-A sets that made up a locomotive of 6,000 horsepower. The vacant number slots between 1404A and 1442B were intended for the remainder of the order, which took until March 1948 to see full completion. The split delivery pattern--first in May 1947, then in October 1947, then from January to March 1948--stemmed from multiple causes: EMD faced a full production schedule; and with training of maintenance personnel taking place, UP did not want more units operating than it had trained personnel to maintain.

UP's first F3 passenger units, numbered as 964A-968A and 969B-978B, were delivered in September and October 1947. These five cab units and 10 booster units were generally used in A-B-B consists on the road's secondary passenger trains on the South-Central District, including the Pony Express and the Los Angeles Limited.

These first units were numbered in the earlier A and B suffix scheme first used on passenger units in 1946, with the group of 30 booster units (1442B-1471B) numbered consecutively after the group of 42 cab units (1400A-1441A). By the time the final units of the order were being delivered in early 1948, UP had ordered an additional group of 36 cab units and 44 booster units. In a change from the earlier A and B suffix scheme, and like other railroads, UP decided to number the A-B-B-A sets in similar and matching number series. The last units of this first order were delivered in this later numbering scheme, with consecutive-numbered cab units, and booster units numbered with the same even-number as the lead cab unit, but with either a B or a C suffix. In this newer system, there were no odd numbered booster units. The first units of the first order, 1400A-1423A and 1442B-1465B became (along with the final units in the order) 1400-1441 and 1400B,C-1428B,C.

By late 1947, UP president George Ashby was very pleased with the road's diesel operation, after the delivery of just two F3 A-B-B-A sets from EMD and five Alco FA/FB A-B-B-A sets for freight service, and five F3 A-B-B sets and two Alco PA/PB A-B-A sets for passenger service. On October 10, 1947, he wrote that diesel operations were proving to be so successful that he recommended the purchase of additional diesel power for the earliest possible delivery. Orders for new locomotives were to be spread among the builders, based on their ability to make early delivery. The purchase of 32 additional 6,000-horsepower freight locomotives would allow diesel-only operations west of Green River, Wyoming, and between Salt Lake City and Pocatello, Idaho. Six 6,000-horsepower passenger locomotives would allow diesel operation of all regular and extra passenger trains west of Green River. Twenty-five 1,000-horsepower switching locomotives would allow substitution of steam in North Platte, Nebraska, and Denver, and in UP's share of Ogden, Utah, operations.

In January 1948, management approved an AFE covering the purchase of 188 diesel locomotives. Included were new Alco road switchers, new Alco, Baldwin, and EMD yard switchers, new Alco passenger units, and 36 F3 cab units and 44 F3 booster units from EMD. These two groups of units from EMD would be used to make up 29 full A-B-B-A sets, including seven as 1550-class units for the Northwestern District, the road's Idaho, Oregon, and Washington Divisions, made up of the former Oregon-Washington Railway & Navigation Co., and the former Oregon Short Line Railroad. Twenty-two other A-B-B-A sets were for the general freight pool west of Green River. Delivery took place between April and December 1948 for the 1400-series units (1442-1463, and 1430B,C-1458B,C), and between October 1948 and January 1949 for the 1550-1563 and 1550B,C-1562B,C groups. The three passenger sets were delivered as 905-910 and 905B,C, 907B,C, 909B,C in May and June 1948. To serve as protection power for all of the road's passenger trains, 12 of the F3 booster units (1430B,C-1440B,C) were equipped with steam generators and water tanks.

The newly delivered F3 units soon took over pulling UP's most important freight trains. One indication was the 46 day period between mid August and late September 1948, as recorded in the Form 2508, Station Record of Train Movement, for Altamont, Wyoming. During one week alone, August 15-21, there were 154 diesel-powered trains, and 26 steam-powered trains; a six to one ratio. The recorded engine numbers also show that UP was very soon mixing the A-B-B-A sets into whatever number sequence was convenient to best suit its daily operations. A similar six to one ratio was shown when comparing the trains powered by EMD cab units, the F3s, with trains powered by Alco cab units, the FA/FB units. In that same one week period in mid August, there were 132 EMD-powered trains compared to 22 Alco-powered trains. (see "Union Pacific Operations at Altamont, Wyoming, August-September 1948" by Frank Peacock, in "The Streamliner", Volume 2, Number 1, page 29)

To better balance the motive power between the South-Central District and the Northwestern District, both being operated by sets of both Alco units and EMD units, UP in 1950 reassigned all of the Alco units to the South-Central District, and all of the EMD units were assigned to the Northwestern District. Included in this change of assignment, and to designate additional units to be assigned solely to the Idaho Division (the corporate entity known as the Oregon Short Line), a group of 29 1400-class cab units and 31 1440-class booster units were regeared, reballasted, and renumbered to the new 1500-1528 and 1500B,C-1530B,C series. These 60 units, along with the other 28 units in the 1550-series, were collectively known as "Short Line" units, and generally operated between Pocatello, Idaho, and Huntington, Oregon. This assignment for these units was possible after agreements with the operating unions on the former OSL that permitted heavier units, allowing heavier trains.

As UP continued to dieselized more of its operations, the road in March 1951 accepted delivery of units that were EMD's improved replacement for its earlier F3 model. These newer units were called F7s, but produced the same 1,500 horsepower as the F3, the major difference being in better traction motors and automatic transition between throttle positions. UP acquired five F7 cab units numbered 1466-1470 and 10 F7 booster units numbered 1466B,C-1474B,C. In October 1951, the road received 10 more F7 cab units, numbered 1471-1480, and 20 more F7 booster units, numbered 1476B,C-1494B,C. From the assigned road numbers, one can see that the F7s were delivered in A-B-B sets.

In late 1951, two F3 cab units and two F3 booster units were wrecked. EMD rebuilt these units and delivered them back to UP in early 1952 as F7 units, numbered as the 1464 set (1464, 1464B, 1464C, 1465).

Always looking for ways to cut costs, UP in April 1952 acquired two cab and booster sets from EMD at a reduced price. The units had been completed for the Mexican National Railroad, which was not in a financial position to accept the units. The two cab units were FP7s, the passenger version of EMD's F7 locomotive, which was four feet longer than a standard F7 to accommodate a steam generator and water tanks. The two matching F7B booster units were also equipped with steam generators and water tanks. These units were delivered to UP as 911, 912 and 910B and 910C.

Also in 1952 UP purchased an F7 A-B-B-A set that briefly ran in an unsuccessful four-trip demonstration in July 1952 on Norfolk & Western Railway (see "N&W's secret weapons" by Robert A. LeMassena, Trains magazine, November 1991, pages 64-69). UP purchased the set prior to their entering service on N&W, getting them at a reduced price. The A-B-B-A set received a new build (and warranty) date of September 1952 and were delivered to UP in December 1952, numbered UP 1481, 1482, 1496B, and 1496C.

(View a photo of the EMD 459 set, taken from Trains magazine, November 1991)

The following comes from the November 1991 issue of Trains, page 64-65:

During July 1952, [Norfolk & Western] 2-6-6-4 1239 made six round-trip test runs between Williamson, W. Va., and Portsmouth, Ohio. These were followed in September by four similar runs by a four-unit Electro-Motive Division F7 diesel-electric. Subsequently the F7 made five test trips from Williamson to Bluefield, W. Va. The F-unit set retreated to EMD's plant at La Grange, Illinois, and N&W behaved as though the steam era would never end.

The 1239, probably recently overhauled, commenced the [July 1952] test program with six runs from Williamson to Portsmouth. The F7's next made four trips, equaling the A's speed with 800 more tons plus a 15 percent saving in fuel. The evidence shows that the F7 set was not an off-the-shelf model with 1500 h.p. engines, but a modified version having 1700 h.p. engines! Back into the shop went 1239, where its boiler pressure was increased to 315 pounds per square inch (psi); there is some evidence that cylinder bore and driver diameter were increased. These modifications increased the tractive effort (and horsepower), requiring 20 tons of lead to be added to the engine's machinery beds to prevent slipping. Three more tests with 1239 (now an unofficial Class "A1") showed that it beat the diesel's speed with 250 more tons, and with only 3 percent added fuel cost. During those tests the 1239 had produced the astounding achievement of 500,000 gross ton-miles per train-hour.

The second battery of tests took place on the steeper grades between Williamson and Bluefield, where the diesel contended with modified compound-expansion 2-8-8-2 2197, an unofficial "Y6c." It had been equipped with a "booster-valve" and a new intercepting/reducing valve which increased the tractive effort by 15 percent and drawbar horsepower by 26 percent. (There is some evidence also that its steam pressure had been increased to 315 psi.) No one really expected a single 2-8-8-2 to equal the F7's; yet, with 300 more tons the steam locomotive showed a 27 percent fuel saving. With heavier trains and lower speeds, however, the diesel's much greater low-speed tractive effort produced a 10 percent saving in fuel costs. This contest ended in a draw; the F7 had not proven any substantial advantage in performance or fuel costs.

After the test programs had been completed neither N&W nor EMD said anything about them; in fact, nothing was ever published, by either company, concerning their outcome. EMD may have been stunned by the inability of its newest, most-powerful locomotive to overwhelm a pair of steam locomotives whose basic designs predated 1930 (the 2-8-8-2) and 1936 (2-6-6-4). What had appeared to have been an easy victory for the "hot rod" F7 had turned into a defeat by the N&W's two "secret weapons." It was not a big defeat, but it was a defeat nonetheless.

A third F7 demonstrator came to UP in January 1953. This had been built in 1950 as one of the earliest F7 cab units, and it entered service on UP as number 1483.

With the final delivery of this last F7, the F7 fleet stood at 20 F7 cab units, two FP7 cab units, and 36 F7 booster units.

Alco FA/FB Units

American Locomotive Co. delivered the first of its new 1,500-horsepower carbody units to Union Pacific in June 1947. By September 1948, the road had received a total of 44 cab units (later known as the FA) and 44 booster units (later known as the FB). These were assigned to operate between Ogden, Utah, Salt Lake City, and Los Angeles. Others were also assigned to operate on the Kansas main line. During the units' first two years, UP tried them in several assignments, including its heaviest main line across Wyoming.

The Alco FA/FB units soon showed increasing maintenance costs. Problems with their diesel engines began to keep them in the shop for extended periods of time. In late 1953, when UP placed an order for 170 GP9s, the corporate board of directors asked why such a large order was going to just one builder. UP President Arthur E. Stoddard, who had succeeded George Ashby in March 1949, answered the query by stating that by mid-1952, the railroad had found that current Alco locomotives cost 41.7 percent greater than EMD; EMD was more dependable; and Alco locomotives already on the railroad required a change out of 75 percent of their components after 150,000 miles, taking 10 days of shop time. This was compared to EMD locomotives requiring only an engine change after 445,000 miles, taking just 20 hours of shop time. Economics was clearly on the side of EMD.

With the arrival of the EMD GP9s in 1954, the Alco units were displaced from their South-Central District assignment and moved to the Eastern District, which was mostly level, and less taxing for the troublesome Alco units, allowing the retirement of still more steam locomotives. At the time of their reassignment, the Alco units were put through a rebuilding program that replaced and upgraded many of their most troublesome components. The heavy shopping was completed at both Los Angeles and Omaha, and corrected many of the problems. The units entered service in Kansas and Nebraska, where they operated in mostly solid sets until the early 1960s, when they started to spend increasing amounts of time in storage lines whenever a downturn in traffic occurred. Because they were not needed by UP, except in the times of heaviest traffic, several were leased during 1963-1964 to Canadian Pacific in southern Ontario, and to Southern Pacific for at least one trip west from Ogden in March 1964. It was reported that the multiple-unit cables on the UP units did not match the MU cables on any SP units, i.e. 21/12 pins versus 27 pins.

Fairbanks-Morse Units

The largest percentage of Fairbanks-Morse locomotives used the 38D opposed piston engine, with 8-1/8 inch diameter cylinders. This engine was developed, along with the 38F diesel engine, with 5-1/4 inch cylinder diameter, in response to the U. S. Navy's need during the early 1930s for a compact, lightweight diesel engine to power its new fleet of submarine boats. This Navy program also led to Winton's 201 diesel engine (later used by General Motors for its diesel locomotives), and Cooper-Bessemer's FW diesel engine, which evolved into the company's FDL diesel engine, later used in General Electric's line of diesel locomotives. (Kirkland, John F. The Diesel Builders, Fairbanks-Morse and Lima-Hamilton, Special 98, Interurban Press, 1985, p. 22.)

The first railroad application of the 38D8-1/8 diesel engine was in a rail motor car for Southern Railway in 1939. (Kirkland, p. 23) The entire Fairbanks-Morse diesel engine production capacity from 1939 on for manufacturing opposed piston engines was taken up to provide the Navy with engines for its submarine fleet, being greatly expanded to protect Atlantic shipping between the U. S. and Great Britain. After the U. S. entry into the war in 1941, the F-M facility was expanded with government financial assistance to ensure sufficient opposed piston engine production capacity to see Allied forces through the war. (Kirkland, p. 26)

By 1943, F-M was seen as having an excess production capacity beyond possible post war projections. This excess capacity resulted in F-M being authorized to begin design and initial production of its own switch locomotive. To expedite this new design, F-M decided to essentially build a copy of the currently available switcher from Baldwin, using its own opposed piston engine in place of the Baldwin De La Vergne design, but still using the same Westinghouse-design electrical gear. (Kirkland, p. 26)

The result of this design effort was the F-M H10-44 1,000-horsepower, four-axle switcher. The first example completed was for the road that directly provided railroad service to the F-M plant at Beloit, Wisconsin, was Chicago, Milwaukee, St. Paul & Pacific Railroad, better known simply as the Milwaukee Road. The locomotive was essentially a Baldwin locomotive powered by the F-M opposed piston engine, and was completed on August 21, 1944. A second example, for Chicago & North Western number 1036, followed in November 1944, and a third was completed for AT&SF in April 1945. F-M's fourth H10-44 (order LD4) was completed for Union Pacific in May 1945 as UP D.S.1300 (the D.S. prefix meaning Diesel Switch).

UP's first Fairbanks-Morse locomotives were a single 1,000-horsepower yard switcher (D.S. 1300) in May 1945. In December 1945, UP received the first three units (the 50M set) of an eventual fleet 13 Erie-built locomotives, including eight cab units and five booster units.

Later, in January and February 1947, the road acquired four more 1,000-horsepower switchers (UP 1301-1304), and in late 1947 and in early 1948, UP received the remaining six Erie-built cab units and four Erie-built booster units.

The three Erie-built passenger units and single switcher gave UP experience with the FM opposed-piston power plant, in service as competition to EMD and Alco, and soon brought additional orders from UP for locomotives with this unique design of prime mover. August 1947 brought five heavy-duty 2,000-horsepower units (UP 1360-1364) for helper service in Southern California. In November and December, six more 2,000-horsepower units (UP 1365-1370) arrived, including two units (UP 1365, 1366) that had been built in June and which had been featured in FM's exhibit at a railroad suppliers' trade show at Atlantic City, N.J. In November 1947, the road acquired four more Erie-built passenger units--two cab units (UP 984A and 985A) and two booster units (UP 986B and 987B).

In January 1948, UP added dynamic braking to five of the 2,000-horsepower units assigned to helper service at San Bernardino and Kelso, California. This feature would reduce brake shoe wear and minimize the hazard of wheel failures due to overheating, when returning light on heavy descending grades. By mid-1948, the FM units had replaced steam locomotives in helper service on both Cajon Pass (San Bernardino) and on Cima Hill (Kelso).

Five 1,500-horsepower F-M road switchers (UP 1325-1329) were delivered in April and May 1948, also for service in Southern California. At the same time, in April and May 1948, four Erie-built cab units (UP 704-707) and two Erie-built booster units (UP 704B, 706B) joined the roster. By this time, the other Erie-built units also had been renumbered in the 700 series. The entire group was converted to freight service in 1953, with the arrival of more E8 units from EMD. The FM units were renumbered to the 650 series at that time.

By 1950, Fairbanks-Morse had begun production of its 1,600-horsepower road switcher, known as the H16-44. In August 1950, UP acquired three of these units, numbered 1340-1342. They were purchased to allow the release of the three of the non-dynamic-brake-equipped 2,000-horsepower units for use in the retarder classification yard at North Platte, Nebraska.

The performance of the FM units was not as successful as UP had wished. In 1950, UP transferred the FM units out of Southern California, and for more than a year, the units were replaced by steam locomotives in helper service. In late 1951, UP took delivery of eight new 2,400-horsepower heavy switcher TR5 cow-calf units from EMD. These newer EMD units replaced the steam locomotives in both helper service and heavy switching and transfer service. The FM units were reassigned to the new terminal in Hinkle, Oregon, and were used in road service between Hinkle and Spokane, Washington. The switchers were moved to the Eastern District. In their final years, during the late 1950s and early 1960s, all of the Fairbanks-Morse units were assigned to the eastern end of the Eastern District. A railfan report from 1961 stated that several F-M units were seen in a dead line in Portland, Oregon, with at least two units being scrapped at a private scrap yard. No specific unit numbers were given.

UP's Erie-built units ended their careers in the Northwest on secondary passenger trains. UP's other Fairbanks-Morse units ended their careers on the railroad's Eastern District. Richard Schmeling remembers them well:

"The UP H10-44s did end their active service life for the UP on the eastern end of the system, but they were not here for very long. The FM power eventually became bunched in the Pacific Northwest and, like the F-units and Alco FAs, as they got older, were sent east to Nebraska to work out their final days before being taken off the roster and disposed of at the Omaha shops. In the early 1960s, the Council Bluffs yard was almost exclusively FM-dominated with the UP 1300-1304 all there and usually one of the H15-44s as well. Although the H15-44s and H16-44s were assigned to Lincoln as the Lincoln switcher, none of the H10-44s made it down here, according to my photo records. Unlike the H10-44s and the H15-44s, the H20-44s were not extensively used in Nebraska before they were retired." (Richard Schmeling, Letter To The Editor, Diesel Era, Volume 4, Number 6, p.56)

F-M Train Master

More research is needed to confirm a verbal statement that in early 1954, Fairbanks-Morse Train Master demonstrators TM-3 and TM-4 spent a day in helper service between Riverdale and Evanston, and then headed east.

In the May 1954 issue of Trains magazine, there is a photo of Fairbanks-Morse Train Master demonstrator TM-4 in Utah's Echo Canyon. The caption reads as follows:

The 2.8 million diesel horsepower placed on order in 1953 - not one new locomotive of any other type was requested for U.S. usage - was not only a better market (the sales total ran to less than 212 million in 1952) but uncorked a number of questions. Topping the list, perhaps, was Union Pacific: what did its unprecedented order for 205 units imply for the 210 modern steam locomotives it has purchased since 1936, much less its older but still big power?

Well, some years ago UP dieselized south of Salt Lake City and practically so west of Huntington, Oregon. From those terminals east to Omaha and Kansas City, though, it continued to operate the bulk of its tonnage and a number of passenger trains behind steam. For UP this policy paid off, at least in freight movement, because of the low cost of company-mined coal from Wyoming. When the price of coal at the pit went up and the mines were occasionally strikebound UP began converting to oil fuel and shortly thereafter the honeymoon was over for steam. When all of its flock of Geeps are in service the road figures on operating some steam on dead tonnage like coal and ore east of Ogden, Utah, and between Huntington. Ore., and Green River. Wyo.

In addition, its roster of 45 Northerns will be kept at work moving second sections, deadhead equipment, express perishable trains and the like. Otherwise. UP is storing all of its 4-6-6-4's, Big Boys and those 4-12-2's which haven't been scrapped to protect seasonal rushes: for the rest -- the Mountains and Mallets and Mikes and 2-10-2's -- the future is without hope. And the Big Show, especially since Sherman Hill has been cut down to size, is over.

Alco-GE 4,500-Horsepower Gas-Turbines

Because Union Pacific was seeking the ideal 6,000-horsepower freight locomotive during 1945, it should not be surprising that when General Electric in 1946 announced that it would pursue gas-turbine technology for railroad applications, UP would be interested. GE intended to apply to stationary power and railroad applications what it had learned in furnishing the first jet aircraft engines. The locomotive application was to be similar to what Brown Boveri of Switzerland had built for Swiss Federal Railways in 1939, and for British Railways in 1940.

GE's partner in the railroad locomotive venture was the same one with which it had teamed since 1940 on a line of diesel-electrics, American Locomotive Co. The first gas-turbine locomotive for the North American market was completed in November 1948, and entered its initial testing phase as Alco-GE number 101, operating on the Nickel Plate and Pennsylvania railroads. In June 1949, GE and UP announced that the double-ended, 4,500-horsepower locomotive would begin an extended test operating as Union Pacific number 50. Tests began right away and continued for 21 months, with the unit running more than 101,000 miles in all types of service, on all major routes on UP.

UP's new Gas Turbine Electric locomotive left Omaha on Saturday July 30, 1949, and arrived in Ogden on Monday August 15th where it was displayed for an hour (9 to 10 am) near the city's Union Station. The locomotive was moved to Salt Lake City and was displayed there on that same afternoon from 3 to 4 pm. Further testing continued after the locomotive arrived in Los Angeles and displayed on August 18th. The tests were to be between Los Angeles and Salt Lake City, and continued through early April 1950 when the Ogden newspapers announced that it would very soon pass through Ogden on its way to additional tests in Wyoming.

In October 1949, representatives from the Western Pacific railroad, and from Southern Pacific were invited by General Electric to observe the Gas Turbine locomotive then being used by Union Pacific on California's Cajon Pass. On October 31, 1949, they inspected the locomotive at Los Angeles, and rode it to Barstow, a distance of 150 miles with a ruling grade of 2.2 percent.

The report, in part, reads as follows.

In conclusion it was the opinion of all the observers from Southern Pacific and Western Pacific that while this locomotive may have possibilities it is still far in the future before many of the objectionable features can be corrected. Some of the objectionable features are as follows:

1) High fuel consumption rated at 1.5 times more than the present diesel power and believe this is a conservative estimate.

2) Terrific noise from exhaust and blower. Normal conversation impossible at 100' from locomotive. This would cause serious complaint in cities.

3) High exhaust temperature - 840F.

4) Horsepower and weight are not balanced because locomotive wheels slip considerably in starting and on heavy grade. Axles are now loaded to 60,000# which is about the limit for track and bridge structures on many railroads.

5) Gas turbine engine can not be started inside shop and has to be taken out in yard for this purpose.

6) One hour preparatory time is needed to start gas turbine.

7) Referring to item 2 and item 5 locomotive could not be used under passenger sheds and in talking to switchmen at San Bernardino they mentioned the noise as being cause for complaint. If three or four such locomotives were standing in yard the noise would be almost unbearable.

The manufacturer and engineers deserve much credit in designing and building this first oil turbine locomotive in an endeavor to perfect a new type of power for railroad use. I understand it took about two years to construct this unit at a cost of more than two million dollars. It is an experimental machine which the manufacturer is testing with the thought of improving and eliminating all possible objectionable features so that it will eventually be a practical unit of power. This admittedly will require a number of years of testing and improving.

(Thanks to Evan Werkema for sharing this information, by way of an email dated June 23, 2019)

UP 50 was returned to GE in April 1951. In December 1950, four months before the tests with UP 50 were completed, UP set aside funds to purchase 10 additional, nearly identical locomotives to operate over its Wyoming main line. The first of this new group, UP 51, was delivered in January 1952, and the last, UP 60, was delivered in August 1953. These first 10 gas-turbines had a full-width carbody and became known as the "Standard Turbines." Fifteen more were ordered in late 1952, but came in a different carbody configuration, which featured outside crew walkways. These 15 units were delivered as UP 61-75 between March and October 1954, and soon became known as "Veranda Turbines."

Propane Tests -- Union Pacific sent its number 57 locomotive to southern California in 1953 for tests to determine if propane could be used on the fleet of new GTE locomotives. The locomotive was equipped with a special pressurized tank car to hold the supply of propane, and the first test was on May 31, 1953, and ran between Los Angeles and Las Vegas, Nevada. The tests lasted until New Years Day 1954 when the turbine failed. The locomotive was removed from service on January 4, 1954 and when repairs were completed soon after, the turbine was returned to using the same heavy fuel as the other locomotives in the fleet. Also, the locomotive was needed for a sudden surge in traffic east out of Ogden. The use of propane as a fuel for gas turbines was successful, but the realities and danger of pressurized tanks holding highly flammable propane, and the added cost of providing a supply of the more expensive fuel to other locations on the UP system made the use of propane impractical. The test between May 1953 and January 1954 saw the locomotive operate a total of 69,600 miles, with 2,961 turbine hours. (The subject of the propane tests, with photos, is covered in Tom Lee's book "Turbines Westward.")

By 1954, these new turbines were exerting a positive impact on UP's bottom line, compared to both steam locomotives and diesel locomotives. During 1954, steam costs were found to be $145.14 per 1,000 gross ton-miles, and diesel costs were set at $84.03 per 1,000 gross ton-miles. The turbines came in even lower, at $69.19 per 1,000 gross ton-miles. But to maintain these lower costs, the turbines had to be running almost constantly, leaving little operational flexibility. Although diesel costs were as much as 20 percent higher, their operational flexibility made them the desired motive power on many trains throughout the Union Pacific system.

Additional statistics for turbine operation showed that they were averaging 8,000 miles and 400 hours per month, with a 78 to 80 percent availability. Union Pacific was very pleased with its gas-turbine fleet, and in early 1956, ordered still more, to be delivered as two-unit, 8,500-horsepower units. These will be discussed later.

August 1956
"Turbines On Top: Union Pacific says that in a typical month of operation (August 1956) its gas turbine locomotives averaged 12,026 miles per unit, which was "considerably better" than any other type of power on the same district. Turbines also averaged 34.95 train-miles per train-hour, which was 6 miles per hour faster than comparable diesels. UP says Big Blows are in no way given preference over other power." (Trains magazine, May 1957, page 10)

September 1956
"Turbine Topics: Just 25 gas-turbines are handling approximately 10 per cent of Union Pacific freight service on a gross ton-mile basis. Nine of the 4500 h.p. GE-built units have 18,000-gallon tanks, could run Ogden-Council Bluffs (990 miles) without refueling; addition of tenders has boosted engine mileage almost 30 per cent per month. General Electric says the GTEL's are "way past the experimental stage," and although they will not supplant the diesel, the Big Blows are excellent for "constant, heavy freight service." (Trains magazine, September 1956, page 10)

Big Blow

The Big Blow nickname for Union Pacific's gas turbine locomotives dates from 1950. According to a news item in the April 4, 1950 Ogden Standard Examiner newspaper, the first use of the nickname for UP's gas turbine locomotives, "Big Blow," was used to describe the double-cab demonstrator locomotive, which ran on Union Pacific as UP no. 50 from late July 1949 to late April 1951. The first UP-owned 4500 HP unit, UP no. 51, came in January 1952.

The term "Big Blow" was first used in a United Press (UP) syndicated story about the new gas-turbine locomotive. The story was picked up by numerous newspapers across the nation, all with April 4th as the dateline. The following comes from the April 4, 1950 issue of the Ogden Standard Examiner newspaper.

'Big Blow' Tested On Wyoming Run -- Rawlins, Wyo., April 4 (UP) -- Wyoming's railroad enthusiasts are watching biggest railroad demonstration in years -- three experimental runs of the Union Pacific's first gas turbine-electric locomotive.

"The big blow," so-called because of its huge size and outlandish noise, will make the three runs between Ogden, Utah, and Cheyenne after the trials now in progress on the Los Angeles-Salt Lake City route are completed, C. B. Lisher, trainmaster for U. P. at Rawlins, announced.

Lisher said runs will be made to determine the practicality of the new-type engine. It has passed preliminary tests satisfactorily, he said. The locomotive first was put on the rails in November, 1948, but experimental runs still are being held.

The 4,500-horsepower mover gets its power from a gas-turbine poser plant, similar to those used in early jet planes.

Fuel is injected to compressed air chambers to set the engine in operation. This burns, and the resulting hot gases expand to push the turbine blades and turn the drive-shaft. The drive-shaft compresses more air, and runs a generator at the same time. Power from the generator drives eight traction motors to put the locomotive in motion. (Ogden Standard Examiner, April 4, 1950)

April 1962
The following comes from The Western Railroader, July 1962:

U.P. "Big Blow" In Southern California. The Union Pacific has been using its turbine locomotives on its California division since April in tests as to their use in this area. Gas turbine No, 60 is run M.U.'d. with regular diesels, but the turbine is shut-down west of Pomona to avoid noise and smog objections. Turbines 30 and 75 have also been used. (The Western Railroader, Volume 25, Number 7, Issue 271, July 1962, page 5)


Union Pacific received 25 of EMD's SW7 yard switching locomotives in August to November 1950.

(Read more about all of Union Pacific's SW7 Yard Switching locomotives)


UP received eight of EMD's TR5 yard switching locomotives in September and October 1951. These were two-unit locomotives made up of a normal cab unit, and a cabless second unit.

(Read more about all of Union Pacific's TR5 Yard Switching locomotives)

One-For-One Passenger Unit Trade-Ins

Between 1953 and 1962, UP received 20 passenger units -- E9s 900-914, E8 925, and E8Bs 922B-925B -- from EMD that were built using direct unit-for-unit trade-ins from UP. Railroad and EMD records both show the trade-in units as being rebuilt to the respective E-units. This rebuilding of an old unit to a new unit is unlikely because the mechanical layout of the early E-units and the "rebuilt" E8s and E9s, were completely different, with almost nothing reusable except truck frames and some minor parts. The rebuilding concept stemmed from a tax advantage that allowed UP, and several other railroads, to pay a reduced tax on the units, since they were "rebuilt" rather than "new." This tax loophole was closed after many industries nationwide began receiving large amounts of "rebuilt" equipment, rather than new equipment.

In the case of railroad locomotives, each unit-for-unit direct trade-in came under EMD's "trade-in credit" policy, which was figured strictly on paper. Due to the short length of time between the trade-in and when the new unit was delivered, and the mechanical differences, it is unlikely that any one part from the trade-in unit was actually used on the intended new unit. It was EMD's practice during E8 and early E9 production to assign the trade-in units' builder's number to the new unit, and to show the trade-in unit's original build date on the builder's plate, even if the new unit was built using as little as five percent of the parts from the older unit, thus UP 922B-925B, and UP 925, were built as new units but were assigned builder's numbers and builder's dates from the original trade-in units. The roster shows the actual build date rather than the build date from the builder's plate.

EMD E8s and E9s

(Read more about Union Pacific's fleet of EMD E8 and E9 locomotives)


Seven of Union Pacific's ten SD7s were purchased in mid 1953 for the Iron Mountain iron ore trains in Utah, along with heavy switching in the Provo, Utah, yard and at the yard adjoining the U. S. Steel plant at Geneva (near Provo), the destination of the Iron Mountain ore trains. The three other units were initially assigned to "to effect economical operation of various branches, other than on the South-Central District." One of these three units, UP 782, renumbered to UP 457, was used throughout its career on the Coalmont Branch, out of Laramie, Wyoming, where it replaced an earlier Alco RSC-2. On that assignment, the unit was equipped with a standby water heater, with its attendant exhaust stack mounted to the upper right hood side near the radiator intakes, and snow plows on each end. The entire ten unit group was renumbered in late 1962 and early 1963 from their original 775-series numbers to the 450-series numbers.

The SD7s were in the Iron Mountain service until replaced in 1968 by new SD45s. At that time, four of the units were reassigned to North Platte, Nebraska, on the new hump yard there. The other five SD7s were assigned to local service between Salt Lake City and Ogden, Utah, and the Clearfield Freeport Center, midway between these two cities. During the 1970s, the Clearfield Freeport Center was the single largest traffic generating point on UP.

Five years after the SD7s began work at North Platte, UP in December 1973 mated SD7 459 with the railroad's first four-axle yard slug. This was soon followed during 1974 by two more SD7s, UP 454 and 458, being paired with the second and third UP-built four-axle yard slugs, with all three slug sets being assigned to North Platte. The SD7s were soon found to be underpowered for this heavy switching assignment and subsequent yard slugs were mated with higher-horsepower SD24s, and later with SD40s.

UP 456 was the first SD7 retired, in April 1978. UP 457, the unit assigned to the Coalmont Branch in Wyoming, was retired in August 1978 following a wreck. Four units followed in 1979: UP 450-453. Two units, UP 455 and 458, were retired in 1980. The last two SD7s to be retired were UP 454 and 459, two units mated with four-axle yard slugs. Both were retired in 1982.

Two of the retired SD7s (UP 456 and 457) were sold to Precision National Corp., and rebuilt to SD10s by ICG at its Paducah, Kentucky, shop. The two units were then shipped in March 1980 to Liberia in West Africa for use on the LAMCO iron ore railroad. UP 453, 455, and 458 were rebuilt by ICG to SD20s, and entered service numbered as ICG 2030, 2034, and 2032, respectively. The remaining five units, UP 450, 451, 452, 455, and 459 were all scrapped following their retirement.


UP received 42 of EMD's SW9 yard switching locomotives in April to November 1953.

(Read more about all of Union Pacific's SW9 Yard Switching locomotives)

EMD GP7s and GP9s

Union Pacific's first road switchers were the Alco-GE RS-2s and RSC-2 s of 1947-1949. Fairbanks-Morse road switchers were delivered in 1948 and 1950, and a Baldwin road switcher also came in 1948. Road switchers were assigned to branch lines as direct replacements for steam locomotives, and with a surplus of steam locomotives available after UP dieselized its western mainline routes, the carrier did not need more road switchers for another two years.

Hoping for an order from Union Pacific, in late 1949 EMD sent its GP7 demonstrator number 200 to work in Salt Lake City. About ten months before, UP had received what would be the last of its F3 road locomotives from EMD, and EMD was selling the road switcher concept as a more utilitarian approach to steam locomotive replacement. Union Pacific apparently appreciated the road switcher design for a little over a year later, in early 1951, UP ordered six Baldwin AS-616 units. Four were purchased for heavy switching, but two others were to be assigned to branchline service in Kansas.

In late 1952, two years after the demonstration of EMD no. 200, UP ordered 10 examples of EMD's then-current road-switcher model, the GP7, which had first been offered in 1950. This first group of ten units was numbered as UP 700-709, and were delivered in February and March 1953. In May 1953, the road ordered 10 more, specifically for service on branch lines in Idaho, and for through train service in Nebraska, Wyoming, Colorado, and Kansas. Two months later, UP ordered 10 more GP7s. These 30 GP7s, originally numbered UP 700-729, were delivered between February and October 1953.

UP's first GP7s were ordered in October 1952 as part of a larger order with EMD that included 22 E8 passenger locomotives (eight A units, to be numbered as UP 931-939, and 14 B units, to be numbered as UP 931B-944B, along with 22 1,200 horsepower SW9 switch locomotives, to be numbered as UP 1825-1846. (AFE 301, approved October 13, 1952)

These first 10 GP7s were originally to be numbered as D.S. 700-709, matching the earlier scheme of designating all switcher and road-switcher locomotives as Diesel Switch units. The decision to remove the D.S. designation was made in February 1953, the same month that the first GP7 was delivered. All ten units were delivered in February and March and may have been delivered with the D.S. prefix. A photo of UP 709 shows the unit with an obvious patch of fresh yellow paint under the 709 road number on the front angled hood end. This may indicate that the unit was renumbered from D.S. 709 to just 709 by UP after its delivery.

There is photographic evidence that the GP7s were originally to be delivered with UP's D.S. road number prefix, denoting Diesel Switch. A photo in the Union Pacific Historical Society's bi-monthly publication, The Streamliner (Volume 11, Number 2, page 26), shows UP 709 with a patch of fresh yellow paint under the 709 number on the front angled hood surface. This means that UP 709 was renumbered from something else, likely D.S. 709. This first group of 10 GP7s were delivered in March 1953, with the order to remove the D.S. prefix having come in mid February. They were renumbered to their 100-series numbers in November 1953. A second photo of an unlettered GP7 painted in UP's yellow and gray scheme, with UP's "Serves All the West" cab-side slogan and taken at EMD's Cleveland factory, shows a unit numbered as 1953 in the number boards, and D. S. 1953 painted on the front angled hood end.

The railroad found these 30 GP7 units to be so cost-effective that in October 1953 it ordered 190 more GP7s, with 115 of them to be built as cab units and 75 as cabless booster units. EMD accepted the order, but since the 190 units would not be delivered until after January 1, 1954, EMD on November 2, 1953, notified UP that a model change was under way and that they would be delivered as some of the first examples of EMD's GP9 model, the GP9 being the 1,750-horsepower successor to the 1,500-horsepower GP7. While EMD had built GP7 booster units for Santa Fe (five units in 1953), these 75 units for UP would be the first cabless booster units of the GP9 model.

After UP sent its order for the additional 190 GP7s to EMD, or maybe at the same time, the mechanical department realized that there were not enough road numbers in the 700-series to accommodate the new units without the numbers running into the 800-series steam 4-8-4 steam locomotives. To change the potential conflict, the 100-series road number group was selected. The 30 GP7s would be renumbered road numbers 100-129. The regular GP9s were numbered upward from 130 to 244, and the cabless boosters were numbered 130B-204B. UP 205-244 were built without dynamic brakes due to their planned assignment to the Eastern District. All were delivered between January and April 1954. As the initial order was arriving, UP ordered an additional 50 units, to be numbered 250-299. These were delivered in August and September 1954. In between were four units that were to be leased to the Camas Prairie Railroad, an Idaho road that UP owned jointly with Northern Pacific. These were to be numbered as UP 245-248. EMD offered GP9 245 to UP at a reduced price because it had undergone a brief demonstration on another road, and UP 246-248 were added to the same order to serve as UP's contribution to the Camas Prairie pool. A fifth unit was needed, so UP offered its number 244. But because UP 244 lacked dynamic braking, it was turned down, and dynamic brake-equipped UP 204 was selected instead. It was renumbered to UP 249 to keep the Camas Prairie units in a single road-number block.

The following is taken from the back cover of the May 1954 issue of Trains magazine:

With faith and confidence in the future, $35,769,410.00 is being spent this year for 205 new diesel locomotives.

Union Pacific demonstrates its firm belief in our nation's progress by continuing its broad program of constant improvement in freight and passenger service.

Of these 205 new diesel locomotive units, 190 will be for freight, and 15 for passenger service.

Delivery is expected to be completed by June 1, 1954, completely dieselizing the railroad's main line between Omaha and the Pacific Coast, for handling of through traffic. Thus, the progressive Union Pacific maintains its tradition of serving all the West with the most modern equipment.

The expenditure of over thirty-five million dollars for these additional diesel locomotives will help maintain payrolls and the buying power so vital to our country's economic welfare.

This large fleet of 275 GP7s and GP9s, along with the road's large fleet of 237 EMD F units, brought an end to steam operations on all but UP's Eastern District. In 1957, UP took delivery on 50 more GP9 cab units and 50 more GP9 booster units, bringing to an end all of the road's regular steam operations, except for some later seasonal use. As UP President Arthur Stoddard wrote in February 1957, these locomotives would allow the railroad to "get by next fall with very little use of steam power." These 100 units, delivered from July through October 1957, were the last diesel units to be acquired until the coming of turbocharged SD24s two years later.

GP9 Turbocharging Program

Union Pacific first tested turbochargers for its GP9 fleet on locomotive 281 in December 1955. It was soon followed by GP9B 185B and GP9 261 in April and May 1956, all three units being equipped with a design developed by the AiResearch Industrial Division of Garrett Corp. of Torrance, California. These three units remained under test, operating in helper service on California's Cajon Pass, and later, between Salt Lake City and Los Angeles, until early 1959. Based on favorable results from these tests, UP began a formal program to add three different turbocharger designs to some of its newest road freight diesels--its 100-unit fleet of 1957-built GP9s/GP9Bs, which had been numbered in the 300 series. Beginning in March 1959 and continuing throughout that year, three A units (302, 318, 331) and six B units (303B, 306B, 311B, 312B, 317B, 348B) were equipped with the AiResearch design. During the same time, UP equipped six A units (306, 310, 314, 315, 324, 336) and four B units (307B, 323B, 324B, 345B) with a competing design that was produced by the Elliott Co. of Jeannette, Pa.

A third design to be installed was EMD's turbocharger, which the builder had developed in response to UP's decision to turn to outside vendors to improve the performance of EMD locomotives. In March 1959, UP sent three units, in an A-B-A set (UP 301, 308B, and 305) to EMD's La Grange, Illinois, plant, to be rebuilt to 2,000 horsepower, using EMD's then-new turbocharger. After being rebuilt, the locomotives were for all practical purposes pre-production GP20s, having been completed six months before the builder's 2,000-horsepower GP20 model was placed in production, since these three units contained all of the same features as the production GP20. Later, in May 1959, UP sent six more units, in two A-B-A sets (UP 300, 300B, 301B, 311, 313, and 320) to EMD to be rebuilt with the new turbocharger. These six units were not outfitted with GP20-style fuel tanks, air reservoirs, and walkway sideframe modifications.

Because of the success of the EMD turbocharger design on the nine units it modified in 1959, UP initiated a program in 1962, which continued until 1966, in which the railroad's Omaha, Nebraska, shops began retrofitting additional 300-class GP9 A units and B units with EMD's turbocharger. The railroad's own shop forces did the work by using parts furnished by EMD. By 1966, the railroad had installed EMD turbochargers in 27 of the 50 300-class A units, and in 27 of the 50 B units. At the same time, again because of the success of the EMD design, two other A units and six other B units that had been carrying AiResearch and Elliott turbochargers were retrofitted with the EMD design, bringing the total 2,000-horsepower GP9 fleet (known as Omaha GP20s) to 29 A units and 33 B units.

June 1959
Souped-Up GP9's: Union Pacific has equipped 25 EMD GP9 roadswitchers with AiResearch turbochargers, hiked unit horsepower from 1750 to 2000-plus. Revamped diesels are said to put out more power at high altitudes; reduce fuel costs; and emit smoke-free exhaust. (Trains magazine, June 1959, page 6)

(Read more about Union Pacific's turbocharged GP9 locomotives)

EMD F9A and F9B

In a continuing effort to upgrade older locomotives, in late 1958, UP contracted with EMD to modernize the road's fleet of 1500- and 1550- class F3s. The rebuilt units were to return to service on the Northwestern District numbered in the 500-class series, a slot that formerly had been occupied by the Oregon Short Line's 2-8-0 Consolidations. The last 500-class 2-8-0 steamers (533, 535, and 537) had been retired in March 1958.

The entire 500-series group of F9s (41 As and 43 Bs) was rebuilt from the remaining fleet of 84 F3s in both the 1500- and the 1550-classes, excluding four units involved in a November 1951 wreck at Orchard, Idaho, which were retired and rebuilt as F7s in 1952. EMD completely remanufactured the 84 units at its La Grange plant. The rebuilding work included replacing the 567B or BC engine with a 567C engine. All-new electrical gear was installed, including new D22 generators and new D47 traction motors. Both the railroad and EMD considered the units to be F9 locomotives, albeit in remanufactured F3 carbodies. The only external indication of the F9 internal components was the 48-inch dynamic brake fan on top and a rearrangement of the carbody side panels to the F9 configuration of a louver set forward of the forward porthole. The class was assigned to the Northwestern District, and the operating department tried to keep them from going either south of Ogden, Utah, or east of Pocatello, Idaho.

The carbody appearance of the 500s varied considerably from one unit to the next, because they were rebuilt from F3s that had been built in 1947, 1948, and 1949. The carbody styles were mixed due to the fact that there was no consecutive or sequential order to either the 1400-to-1500-series renumbering, or the 1500-to-500-series rebuilding. Because of this, the only accurate method to determine the carbody style exhibited by any particular 500-class unit is to examine a photograph of that unit.

(Read more about what to call UP's 500-series locomotives)

GE UM20B Cab Units

Following the break-up of a longstanding joint marketing and production consortium between Alco and GE in 1953, General Electric began design work on its first road locomotives. In September 1954, the builder completed a set of two cab units and two booster units. As built, all four units were equipped with Cooper-Bessemer diesel engines; the 750A and B carried 1,800-hp, 12-cylinder engines, while the 750C and D carried 1,200-hp, eight-cylinder engines. All four units were propelled by GE Model 752 traction motors. During their rebuilding in 1959, all four were equipped with 2,000-horsepower 12-cylinder Cooper-Bessemer engines.

The completed set of two cab units and two booster units was leased to the Erie Railroad from 1954 to 1959. While GE tested the design, the set ran in revenue service as Erie 750A and 750D (cab units) and 750B and 750C (booster units). In mid-1959, all four units were returned to GE for design improvements, and when completed, they carried the designation of model UM20B (U for Universal, M for Modified, 20 for 2,000 horsepower, and B for B-B trucks).

Union Pacific purchased the four locomotives on October 21, 1959, numbering them 620, 620B, 621, and 621B. After delivery in April 1960, they remained in service for a brief 3-1/2 years, but during their early years, they proved that GE was indeed capable of building reliable diesel road locomotives (Apart from its joint work with Alco, GE's previous expertise in the locomotive field was limited to electric locomotives and very light diesel switchers).

The following comes from a Union Pacific internal communication dated October 28, 1959:

For your information, have received advice that Union Pacific has recently purchased from General Electric Company an 8000 HP G.E. locomotive which was built in 1954 and used as a demonstrator, however, it has been completely rebuilt by General Electric and carries the new locomotive warranty.

Locomotive consists of 4 units, 2 "A" units and 2 "B" units of 2000 HP each. Each unit is powered by one 12-cylinder, 4 cycle, Vee-Type turbocharged Cooper-Bessemer engine rated at 2000 HP at 1000 RPM.

The units are equipped to operate on either diesel or residual type fuel and are arranged for M.U. operation with EMD or Alco units.

Unit numbers will be 620, 620B, 621 and 621B.

While these four units had been testing on Erie, GE had also undertaken a major redesign of the Cooper-Bessemer engine, completing its first 16-cylinder version in July 1958. In 1959, the builder completed two 2,400-horsepower prototype road-switcher units to further test its design concepts. These two units were originally built as export demonstrators (called XP24), but were changed to domestic units, designated U25Bs in 1960, and given GE numbers 751 and 752.

(Read more about Union Pacific's sixteen GE U25B locomotives, delivered in August 1961.)

These four unique GE cab unit locomotives were in service on Union Pacific from April 1960 through October 1963, just 3-1/2 years. Photographs of them in service are very rare.

(View a photo of one of the cabless booster units, UP 621B; photo by Union Pacific)

(View the roster listings for these four unique locomotives)

GE 8,500-Horsepower Gas Turbines

(Read more about the "Big Blow" nickname for UP's gas turbine locomotives; first used in April 1950)

Following the success of the 4,500-horsepower Standard and Veranda turbines, delivered in 1952-1954, UP in 1955 ordered additional gas-turbine locomotives from GE. Changing design features and developmental problems delayed their delivery until August 1958.

UP locomotives 1-30 were three-unit 8,500-horsepower Gas Turbine Electric (GTE) locomotives built in A-unit, B-unit, and tender configuration. The A units held the cab, all controls, and a Cooper-Bessemer FWB-6 850-horsepower diesel engine to power the auxiliary mechanical devices, and to act as motive power for short movements in yards and terminals. The B units held the gas turbine itself and four massive electric generators, which generated the power for the 12 traction motors, six each under each A unit and its corresponding B unit. The tenders were electrically heated (and some were insulated) and held 24,000 gallons of heavy residual (which many mistakenly call "Bunker C") fuel. They were rebuilt from steam-engine tenders that had once trailed 800-class 4-8-4s and 3800-class 4-6-6-4s.

(Read more about Bunker C fuel oil)


As with the smaller GTE 4500 turbines, cost studies showed that UP had to keep these larger GTE 8500 locomotives moving, to extract the greatest cost benefit from them. However, increasing maintenance costs and a growing lack of reliability kept many of them in the shops. Also, the price of the heavy fuel that the turbines depended on, was increasing as the refineries found more profitable uses for this residual fuel.

By the mid-1960s, more and more of the units were spending time in dead lines. The first of the 8500 GTE locomotives was retired in August 1968, and others followed in 1969 and 1970. Most of the units retired in 1968 and 1969 were traded to General Electric, which used the turbines' three-axle trucks under the double-engined 5,000-horsepower U50C. The remainder, and the units retired in 1970, were sold to Continental Leasing, which scrapped the cab units, and stripped the turbine-generator sets from the B units for use as stationary power plants. The units traded to GE also saw the same use for their turbines. Several of these turbine-generator sets were used very successfully as stationary power plants on dredging barges constructed by Intercontinental Engineering, suggesting that the actual turbines were the reason that the company had purchased the gas turbine locomotives.

(Read more about UP Turbines At The End)

August 1960
GTEL Report card -- The word is that one of Union Pacific's 8500 h.p. gas turbine-electrics can lift 6740 tons up a ruling grade of 0.82 per cent with a minimum speed of 18.4 mph vs. a rating of 7320 tons for four 2400 h.p. SD24 diesel hood units. The big turbines' fuel costs are running slightly higher than those for diesels, but the GTEL's "digest" residual oil better than the diesels. One drawback: When turbine is shut down, there is no dynamic braking available on the 8500 h.p. jobs. As to the older turbines: UP's 25 4500 h.p. GTEL's ran off 13.2 per cent of the road's freight gross ton-miles last year but 20 per cent of that can be credited to the Geeps with which the GTEL's are often M.U.'d. (Trains magazine, August 1960, page 12)

10,000 Horsepower

The 10,000 horsepower figure was the result of a few tests, and very few of the three-unit gas turbine locomotives actually ran at the higher horsepower for anything more than tests. And the entire fleet was constantly under test, always looking to improve performance in hopes of proving the concept. By the late 1960s fuel simply got too expensive, and the high maintenance costs finally brought the demise of the gas turbine fleet. Also, many of the people who originated the gas turbine concept, and maintained them in the field, were retiring (especially the man at the top, D. S. Neuhart). By the late 1960s there wasn't the knowledge base or will to keep them running.

The best source is Tom Lee's book, Turbines Westward. He had access to Union Pacific documents, and knew many of the people at UP who were involved with the gas turbine project. All others are railfan rumors.

Tom Lee wrote.

The first of the "Super Turbines" made its initial trip west from Omaha on August 31, 1958. The last, #30, was delivered in late June 1961. Only a year later, a program of upgrading was started that resulted in the original 8500 horsepower rating being increased to 10,000 horsepower for many of the locomotives.

The motive power records always indicated that these locomotives were rated at 8,500 horsepower. The turbine prime-mover had a 10,700 horsepower rating, producing 8,500 horsepower input to the generators and 7,000 horsepower at the rail. The 8,500 horsepower rating was arrived at for ambient conditions of 6,000 feet elevation and 90 degrees Fahrenheit. As would be expected, the horsepower output of these locomotives varied considerably at times due to both changes in ambient factors and the locomotive's mechanical condition.

Tests were made in which 10,000 horsepower was obtained with the excitation controls set up. This would tend to overload the electrical equipment causing subsequent damage when allowed to continue. Therefore, for all practical purposes, the big turbines were rated as 8,500 horsepower locomotives, with actual horsepower output varying higher or lower due to several possible conditions.

Coal-Burning Turbine

Union Pacific's coal-burning turbine, a two-unit set with road numbers 80 and 80B, was built by the road's Omaha Shops over a more-than-two-year period, between September 1959 and December 1961. Stationary load testing took place at Omaha between December 1961 and mid-October 1962, with limited road trips taking place between Laramie and Rawlins, Wyoming, on January 16 and April 7, 1962.

The control unit was rebuilt from UP Alco 2,000-horsepower PA-1 passenger unit number 607, which had been retired in March 1961 and sent to Omaha Shops for conversion (UP 607 wasn't actually renumbered to UP 80 until October 1962, when the rebuilt locomotive entered revenue service). Modifications to the Alco passenger unit included removal of the steam generator and main air reservoirs from the rear interior of the unit, and installation of an additional 3,852-gallon diesel fuel tank. The air reservoirs were re-installed along the roof.

The second part of the set, the turbine-containing unit, was built using the frame and running gear of Great Northern Railway W1-class electric locomotive 5018, which UP had purchased at scrap price from GN in September 1959. The turbine on the B unit was essentially the same as the type used on UP's road numbers 61-75 "Veranda" gas-turbines, with modifications to burn coal completed by Alco.

A tender for the set was rebuilt from the retired 14-wheel "Centipede" tender off a UP 3990-class 4-6-6-4 steam locomotive. It contained storage space for 61 tons of nugget coal, and equipment needed to crush and process the coal to a flour-like powder to allow the coal to be pumped as a fluid to the B unit for fuel.

The locomotive underwent modification and testing between January and October 1962, when it was placed in revenue service. On October 17, 1962, it made its first road trip between Omaha and Grand Island, Nebraska. It ran in revenue service from October 17 to November 15, operating between Omaha and North Platte, Nebraska, or between Omaha and Cheyenne, Wyoming, accumulating a total of 3,000 miles. From November 16 to March 24, 1963, the locomotive was in Omaha Shops for further modifications and more stationary load testing. On March 25, it was placed back in revenue service between Omaha and North Platte, or between Omaha and Cheyenne, accumulating 8,698 miles by July 1, 1963. It continued in service until May 12, 1964, when it made its last revenue trip, after which it was removed form service and stored.

To avoid road-number conflicts with newly ordered DD35s, UP 80 and 80B were renumbered to 8080 and 8080B in April 1964, while the locomotive was making its final runs (DD35 80B was delivered in June 1964). The B unit and tender were retired and scrapped by Omaha Shops during 1967. In March 1968, the A unit was retired and a month later, in April, was sent to EMD as trade-in on an order for new SD45s.

The coal-burning turbine tests were unsuccessful because of excessive wear of the turbine blades caused by the fly ash from the coal, and also because of problems that surfaced in moving a dependable, continuous supply of pulverized coal from the tender to the turbine unit. After being stored in Council Bluffs, Iowa, the set was retired and never ran again.


After EMD perfected its turbocharger in 1958, UP was one of the first roads to acquire the first locomotive model on which EMD mounted the device as standard equipment--the 2,400-horsepower SD24 design. EMD completed its first SD24 in July 1958, just after it had successfully completed tests on its turbocharged engine design. The first customers for the SD24 were Santa Fe and CB&Q, both in May 1959. Union Pacific's 30 SD24 units were delivered beginning in July 1959, numbered as 400-429. UP was the only road to purchase SD24 cabless booster units, which were delivered at the same time as the cab units. The booster units, of which there were 45, were numbered 400B-444B.

At the time that UP ordered their 75 SD24s, they also announced that the reason for such a large order, at $19 million for the total order, was that the new turbocharged design would allow UP to burn residual fuel in these turbocharged locomotives. Similar to the use of residual fuel in its new gas turbine locomotives, Union Pacific expected lower operating costs by burning the low-cost fuel in its new SD24s. (Trains magazine, May 1959, page 25)

Following their delivery from June to September 1959, and for the following 10 years, UP's SD24s predominated as freight power over the road's South-Central District (the former Los Angeles & Salt Lake Railroad), between Salt Lake City and Los Angeles, through Las Vegas and southern Nevada. They usually operated in six- to eight-unit sets of two cab units with four to six booster units in between. Their delivery augmented the already existing large numbers of GP9s assigned to the district. The SD24s also allowed UP to eliminate the two major helper districts on the line, Cajon Pass and Cima Hill, both in California, with grades as steep as 2.2 percent.

In 1969 and 1970, with the arrival of 6900-series DDA40X Centennial units, UP reassigned the SD24s to the general motive power pool. But their unique low-speed pulling power was soon assigned, in 1971, in sets of eight (four cab units and four booster units), to U.S. Steel's Atlantic City (Wyo.) taconite iron-ore unit train that operated between the Atlantic City mine in central Wyoming and U.S. Steel's Geneva, Utah, steel mill. The units in Atlantic City taconite service were bumped in 1974 by UP's unique SD40X units. Others were assigned to switching service in large yards such as Los Angeles and Ogden, Utah, as well as to hump yards in Pocatello, Idaho, and North Platte, Nebraska. Several cab units were retired in 1977, and still more in 1980-1982. The last units, assigned to switch service, stayed in service until 1985. The cabless booster units were all retired in 1977-1981.

Alco/EMD RS-1m

January 1960
"New Home For The Hybrid: Union Pacific, a railroad known for variety in motive power, has picked up an odd one: Bamberger Railroad diesel 570, now UP 1270. Bamberger (which folded last year) got the early road-switcher from Alco-GE in 1943. Although the few units built up to that time had been partly requisitioned for wartime use in Iran, the Utah electric rated one complete with heating boiler (and a trolley pole to throw signals) for its troop trains. The Alco's silhouette became truly unforgettable in 1951, when upgrading at La Grange gave it an EMD hood." (Trains magazine, January 1960, page 14)


Union Pacific acquired 30 units of EMD's latest four-axle offering, the 2,000-horsepower turbocharged GP20 model, in July and August 1960. But the road was already familiar with the design because of its earlier tests with AiResearch and Elliott turbochargers and its collaboration with EMD on that builder's new turbocharger. UP retrofitted turbochargers on some of its GP9s in its Omaha Shops, and sent nine of its GP9s to EMD for retrofitting. After these units were modified, all of them became, in function and in specification, GP20s, but they retained their GP9 road numbers.

Formal GP20 production began in September 1959 (with six-axle SD24 production having started in May of that year). The first customer for the GP20 model was Western Pacific, in September. As noted, UP received its GP20s beginning in July 1960. As delivered, the 30 units were numbered 700-729. This series lasted for 2-1/2 years, until December 1962 and January 1963, when UP renumbered them in anticipation acquiring 35 newer GP30 units that were to be numbered in the 700 series, adjacent to the 800-series GP30s already on the railroad. UP renumbered its 30 production GP20s to 470-499.

(Read more about UP's GP20s)


In September 1961, Union Pacific purchased four former Alco RS-27 demonstrator units, built under Alco's DL-640 specification. Originally numbered as Alco 640-2 to 640-5 (Alco 640-1 was sold to Pennsylvania Railroad), these four units had been completed in December 1959 and January 1960, and were part of the total production of 26 units, built between 1958 and 1962. They were the first Alco units purchased by UP since the last PA passenger unit in January 1949, showing that UP had a long memory concerning the mechanical troubles of the earlier Alco units. Purchased at a bargain price (UP owned more former demonstrator units than any other road), UP numbered the units as UP 675-678, and the units were generally assigned to the Eastern District, usually on the Kansas Division between Denver and Kansas City. The first unit to leave the roster was 677 following a wreck on November 23, 1968 at Aikens, Kansas, which was also the cause for the retirement of U25B 627. The other three RS-27 units were retired in 1971 and sold for continued service on smaller mining railroads.

GE U25Bs

In 1959, General Electric completed two 2,400-horsepower prototype road-switcher units as a further test its design concepts, which included a 16 cylinder version of its Cooper-Bessemer diesel engine. These two units were originally built as export demonstrators (called XP24), but were changed to domestic units, designated U25Bs in 1960, and given GE numbers 751 and 752.

With the success of the XP24 prototype units, GE completed four of the later U25B design to serve as demonstrators. These were numbered GE 753-756, and later sold to St. Louis-San Francisco Railway. While they were in service as demonstrators, their brief stint on UP impressed the road, which soon placed an order for four units. Delivered in August 1961, they were the first U25Bs built after the demonstrator units. Given road numbers 625-628, these four units were equipped with high short hoods, as were a second group of four units, UP 629-632, that was delivered in May 1962.

After selling its first demonstrator set to Frisco, GE completed a second set in February 1962, numbered as GE 2501-2504. The builder in July 1962 sold these to UP, which numbered them 633-636. Three of the demonstrators also had high short hoods. GE 2501 (the later UP 633) was built with a low short hood, a design similar to the low noses EMD had furnished earlier to UP on new GP20s and SD24s. In August 1962, GE delivered four more low-nose units to UP (numbered 637-640), raising the road's U25B fleet size to 16 units.

All 16 units were used systemwide in general pool service for about 10 years. By the late 1960s, the U25Bs were among the first units to be stored every time there was a traffic downturn, and in September 1972, barely 10 years after they gained the distinction of being the first U25Bs to be built, they were the first U25Bs to be retired. In 1968, UP assigned units 633, 638, 639, and 640 to hump service at Pocatello, Idaho, replacing retired Baldwin AS-616 units. UP 632 was rebuilt with a 12-cylinder engine in April 1969, testing the design that would be installed later that same year in new U50Cs.

EMD GP30s and GP30Bs

After testing the GP22 (later changed to GP30) prototype unit, EMD 5629, in 1961, Union Pacific ordered 75 production versions to be numbered as 800-874. This first group of production GP30s was delivered in July and August 1962. The GP22 prototype was rebuilt as the GP30 demonstrator, and UP purchased this unit in September 1962, renumbering it 875. Thirty-five more GP30s were delivered in February and March 1963 as UP 700-734, with a single additional unit, UP 735, delivered in June 1963 (built with a wrecked F9 as a direct trade-in). As with the earlier SD24s, Union Pacific ordered cabless booster versions of the GP30 model. These unique-to-UP locomotives were delivered as units 700B-739B from April through July of 1963. The last 13 of them, numbers 727B-739B, were delivered equipped with steam generators for use as standby passenger units, and for service on special movements such as mail and express trains, and on the movement of circus trains visiting cities along UP's route.

For the first seven to eight years, the GP30s were used on the road's priority trains, operating between its eastern terminals and terminals on the west coast. With the arrival of six-axle high-horsepower SD40s in 1966, some GP30s were bumped down for regular assignment on some of the road's secondary freights. With the SD40s themselves bumped down to secondary service after the delivery of DDA40X Centennial units and SD40-2s, many of the GP30s entered branch line and local service, and some became switchers in the larger yards.

Spokane International Alco RS-1s

In 1962 Union Pacific leased the 12 Spokane International Alco RS-1 locomotives, built as Spokane International Railway 200-211 in 1949 and 1953. On October 6, 1958, Union Pacific purchased 99 percent ownership of Spokane International. The road continued to operate between Spokane, Washington and its connection with Canadian Pacific using the original locomotives. In 1962 the operations were changed to use more powerful Union Pacific locomotives and the 12 SI units were leased to Union Pacific. UP repainted them to UP's standard yellow and gray paint scheme, with Spokane International spelled out in UP's rounded Gothic style lettering. The RS-1s were moved by UP to its Eastern District and were assigned to Colorado, as well as Lincoln, Nebraska, during 1962, and Kansas City during 1967.

An example of the units' early assignment in Colorado was on a day in December 1962, when the dispatcher's sheets show that SI 1214 and 1216 were both working on the "LaSalle Switcher" that day. Switchers based out of LaSalle, Colorado worked the various northern Colorado branches and customers along the mainline.

Proposed 5,000 Horsepower Locomotive

Don Strack wrote about UP's proposed 5,000 horsepower in February 2014:

Back in 1978, I spent an evening with Harold Rees, UP's Mechanical Engineer in the Motive Power & Machinery Department. It was at the invitation of Lloyd Edson, who had been field engineer in 1955-1960 for UP's turbocharged GP9 project. I had met Lloyd while I was working for UP in the Salt Lake diesel shop, and asked what he knew about the turbocharged GP9 project. I was quite surprised when he said, "I made it happen." He invited me to Omaha, and six months later, I was there in his office. Lloyd was the field engineer for the turbocharging effort in 1955-1960, which came to an end when UP got EMD's attention about turbochargers and offered the SD24 and GP20s. Lloyd introduced me around, including a quick visit with Frank Acord, the top man in UP's MP&M Dept. Lloyd invited me for an evening at his home, and mentioned that he would also invite Harold Rees, who Lloyd said had been his mentor.

Harold Rees had retired a couple years before, but had been Lloyd's boss back in Omaha during the GP9 project. They were both mechanical engineers. Harold brought several items with him that evening, including a file covering his work designing and building UP's two diesel-electric snow plows (9000080, built in 1959, and 9000081, built in 1966). There were several other items from his days as a design engineer with UP, including his work designing UP 80, the coal turbine, and his work throughout the 1950s as D. S. Neuhart's design engineer for UP's locomotives and cars.

At the end of the evening, Mr. Rees simply gave me the whole thing, "Here, you take this." Among those items was a drawing of UP's specification for a 5000 horsepower locomotive, dated December 4, 1962. This is what resulted in the GE U50 (delivered in 1963), the EMD DD35 (delivered in 1964), and the Alco C855 (also delivered in 1964).

This is where it gets embarrassing. This drawing was in the file for the snow plows (my current project), and I just discovered it earlier this week, 35 years later. I sure wish I had it at hand when I did the article in Diesel Era magazine back in 2001 ("Union Pacific DD35s" Diesel Era, Volume 12, Number 1, January/February 2001).

Here is a link to the drawing, in all its high-resolution glory:

Union Pacific's Proposed 5,000 Horsepower Locomotive

EMD DD35, ALCO C-855, and GE U50 Double Diesels

In its search for its ideal three-unit 15,000-horsepower locomotive, Union Pacific in 1963 purchased EMD's DD35s, GE's U50s, and Alco's C855s, all of which were delivered in 1964 and 1965. These were the first of UP's trademark "double diesels." While all three designs met the requirements of the conceptual design, the reliability of the GEs was disappointing, and that of the Alco units was even more so. Having just entered the road-locomotive market on its own two years earlier, General Electric was eager to build reliable units, and its post-sale customer service reflected that, with much time being spent fixing the U50's reliability problems. The three designs were a direct result of studies by the road's own mechanical staff during 1962, which had shown that bigger was better. These studies showed that no matter how large or small a locomotive's horsepower rating was, the annual per-unit maintenance cost was $7,000. Having developed this bit of data, Union Pacific decided that to meet its future motive power needs, it would purchase large-unit, high-horsepower locomotives.

The first examples of General Electric's offering, the U50, were delivered in October 1963 as UP 31, 32, and 33. These units, along with the Alco units delivered in June 1964, as UP 60, 60B, and 61, rode on the twin two-axle span bolster trucks from retired Standard and Veranda 4500 GTE locomotives. The reliability of the Alco units was unsatisfactory, but more GE U50s were delivered in from July through September of 1964 (12 units, UP 34-45), and again from May to August of 1965 (eight units, UP 46-53), making a total of 23 5,000-horsepower GE units.

EMD delivered 25 DD35 cabless booster units from May through September of 1964, numbered 74B-98B. EMD had built two original DD35 demonstrator units in September 1963, along with two accompanying GP35 cab units, and sent this GP35-DD35-DD35-GP35 15,000-horsepower set to several other roads to demonstrate the concept of large, high-horsepower locomotives. UP purchased the demonstrators in May 1964 along with the first of its 25-unit production order.

When UP had asked the three builders in 1963 to build these three designs, the road had suggested the span-bolster style of suspension that GE and Alco ultimately used on their units. EMD chose to furnish its units on an all-new, four-axle design--D-D trucks, using the AAR designation for four powered axles. UP was so pleased with its 27 DD35 units that it ordered 15 more of them, but equipped as cab units; they were delivered from April to June 1965 and numbered 70-84. The first 14 of these units were unusual in that they were powered by GE traction motors from trade-in Alco FA/FB units that UP had purchased in 1947-1948. The fifteenth unit, UP 84, was equipped with the traction motors of wrecked trade-in GP9 159.

All of these double-diesel units were used systemwide during their early years of service. The Alco units were the first to be removed from service, after being restricted to the Eastern District soon after being built. They were retired in 1970, just six years after delivery. The GE units also tended to stay on the eastern end of the system, but were used regularly on trains all over the system. It was the 42 EMD units that were able to work on any train the road wanted them for, and they continued in mainline service for over 15 years, being retired in 1979 and 1980.

One of the most noticeable features of these EMD units in their later years was the addition of external sand boxes. Of necessity, when these units were built, their electrical cabinets were located at the ends, as were the sand boxes. As the units aged, the sand boxes began developing minute fatigue cracks that allowed very fine and gritty dust to enter the electrical components, causing excessive wear and electrical problems. To combat this dust problem, UP began relocating the sand boxes to the units' walkways, using a design very similar to that used on the DDA40X Centennial units.

(Read more about Union Pacific's DD35 locomotives)

U50 or U50D

The following was a letter from Don Strack to the editor, published in The Streamliner, Volume 18, Number 4, Fall 2004, page 6:

I enjoyed the recent article on Union Pacific's U50 locomotives (Union Pacific's Whirlybirds, The Streamliner, Volume 18, Number 3, Summer 2004, page 24). The photos were great, and I learned a couple things from the text. However, there is a small problem with the model designation that slipped into the article in a couple places, and on the issue's cover.

Nowhere in all of my research have I seen these units referred to as anything but U50, or U-50. The U50D designation is purely a railfan invention from the 1970s, and was a good-willed attempt to differentiate these B+B units from the later U50C units. As near as I can tell, the U50D designation was first used in 1969. It was not in the Motive Power Review, 1968-1977 book, published in 1978, which used the U50 and the U50C designations. A mix of the two terms was used by George Cockle in his "Giants of the West", published in 1981. In his book "Union Pacific, 1977-1980", published in 1980, George Cockle writes about the apparent confusion by railfans between the earlier U50 and the later U50C, saying on page 16 that rather than using the more correct B-B designation, the earlier units were identified as U50D, which implies that these units were equipped with a one-piece, four-axle truck, which they were not.

The first railfan report of a U50D that I can find was in the September-October 1969 issue of Extra 2200 South, on page 12. The U50D designation was made by the magazine's editor, Don Dover, in his on-going efforts to clarify the confusing combinations of letters and numbers that make up the model designations from all locomotive builders. Unlike the builders and railroads, who only had to deal with a limited numbers of locomotive model designations, as a magazine editor, and an historian, Mr. Dover was concerned with all builders, and all locomotive models, from the first diesels in the late 1920s through to modern times.

Writers of Union Pacific magazine articles and books soon embraced Dover's U50D designation, the most active being George Cockle in his books and articles of the early 1980s. I used the U50D designation in my very first UP diesel roster completed in September 1978, in the form of a 62-page typewritten manuscript that was published as the first illustrated all-time Union Pacific diesel roster, in five issues of Extra 2200 South in 1979 and 1980. That roster used the slightly modified "U50(D)" designation, along with continuing to use the correct U50 designation. The U50D designation appears to have become more completely embedded with the release of Overland Models' imported brass model, and the accompanying magazine ads. The earlier version from ALCO Models used the more proper U50 designation.

By the late 1980s, and with the retirement by UP of these wonderfully unique locomotives in 1973, 1974, and 1977, interest by writers fell by the way side. Since the early 1990s, as interest increased for an updated Union Pacific roster making use of computer technology, there has been an effort by railroad historians to use information as used by the railroad equipment builders or by the railroads themselves, rather than railfan data, or data and designations from outside of the railroad industry. General Electric's own documents do not use anything other than U50. Neither does any Union Pacific document or drawing.

Similar instances occur with Union Pacific's 500-class F9 units. The use of F9AM, or F9BM (like in Thorton Waite's fine Spokane International article) is purely a railfan invention. They were not modified F9 units, nor were they upgraded F3 units. They were new F9 units. Union Pacific and the builder, EMD, always referred to these units as F9s, because that's what they were. True, they were built using major portions of the carbodies of various configurations of trade-in F3 locomotives, but all internal electrical and mechanical components were new. To save money on the overall contract, the builder did reuse the truck frames, and reconditioned and re-qualified cores of some of the trade-in traction motors and radiator fans. Research in original documents shows that these 500 series locomotives were considered by both UP and by EMD only to be new F9 locomotives.

As mentioned in the article, the "Whirlybird" nickname comes from the large radiator fan, located just under the radiator section at both the front of the unit and the rear of the unit. The fans were very large (about six feet in diameter), and as crew members entered the cab from either of the two side doors, they passed by the rotating fan, with only the protection of the open-wire grille. Like all early GE radiator fans, the fans on the U50s were mechanically driven, and were operating at all times. This nickname is mentioned at the top of page 158 in George Cockle's great book, "Giants of the West". The large, rotating fans reminded almost everyone of whirling helicopter blades, hence the "Whirlybird" nickname. The units were also known as "Rock Crushers", due to the large and noisy squirrel cage traction motor blowers immediately below the radiator fans. The photo at the top of page 158 in George Cockle's book shows the traction motor blower very well.

Proposed Gas Turbine

SKY'S THE LIMIT: Pratt & Whitney, the aircraft engine people, have been talking to Union Pacific about a 16,000 h.p. gas turbine-electric. Such a power plant could be mounted in two of the older GE-built 4500 h.p. turbine carbodies. UP also reportedly is buying more than 50 5000/5500 h.p. twin-engined diesel-electrics, and Espee is rumored to buy some too. (Trains magazine, January 1964, page 11)

The first of the twenty-five 4500 HP GTELs, a group of seven locomotives numbered as UP 51-57, were retired in 1962. In 1963, eleven units were retired (UP 60-66, 71-73, 75), and in 1964, the remaining seven units (UP 58, 59, 67-70, 74) were retired.


Of the 24 GP35s delivered to Union Pacific in 1964, two were notable as the first two of total production of over 1,300 GP35s. Intended as an improved GP30 (with its 2,250 horsepower), the 2,500-horsepower GP35, with its features that included easier maintainability, was introduced to the nation's railroads in September 1963 as part of a massive 15,000 locomotive set that included two GP35s (which became UP 762 and 763) and two 5,000-horsepower DD35 booster units (which became UP 72B and 73B). The set, painted in a striking orange and white paint scheme, toured the country, but only UP and SP bought the double-engined booster units. Other roads saw the potential of the single 2,500-horsepower unit and eventually 1,333 units were sold to U. S., Canadian, and Mexican railroads, with the GP35 remaining in production until December 1965, when it was replaced in EMD's catalog by the 3,000-horsepower GP40. UP purchased its two former demonstrator GP35 units in May 1964, along with the two DD35 units, after the four units had completed their nationwide tour. The follow-on order for 22 additional GP35s were delivered in May and June 1964 and saw service system wide. Although the demonstration set operated in its initial GP35-DD35-DD35-GP35 configuration, and as dramatic as the set may have appeared to interested observers, the reality of day-to-day operation seldom saw a similar consist of locomotives in normal road service. By late 1982, only four of the original 24 units had been retired. The other 20 units were active and many were being used in either local service or were in switch service at many of the road's smaller terminals where the added flexibility of road units were needed instead of dedicated switcher designs.


The ten SDP35s UP acquired in 1965 were intended for passenger service (they were purchased just 18 months after the newest E9s), and later exhibited the same electrical problems that were common to all of EMD's 35-line locomotives. UP assigned its SDP35s to the Eastern District (Nebraska and Kansas Divisions), keeping them close to Omaha for use in special passenger moves. UP's SDP35s were used, along with steam-generator equipped GP30Bs, on Vietnam-era troop trains. These troop trains operated between Fort Riley, Kansas, and the West Coast. Three SDP35s were used at least once on the "Snowball Express" ski trains between Salt Lake City and Park City, Utah, located in the high Wasatch Mountains of northern Utah.

One of the unique features about UP's ten EMD SDP35 locomotives was their rear MU connections. In addition to the usual lower MU connections below the walkway, these locomotives had a second set of MU connections mounted up on the rear of the carbody to match the high MU connections on any following EMD E8 and E9 locomotives, which had their MU connections on their noses, adjacent to the headlight.

Some observers have remarked that, because UP had a surplus of E8s and E9s, the SDP35s were seldom, if ever, used in normal operations on its Streamliner passenger trains. Art Gibson wrote in February 2007 that on at least two occasions, and likely many others, UP used the SDP35s on its Streamliner trains in Kansas. On June 15, 1970, Train No. 9 at Topeka, Kansas, had UP 932 and 1401 as power, along with baggage 6334, sleeper 1409 "Pacific Cove", diner 4803, dorm lounge 6103, and coaches Milwaukee 623, UP 5444 and 5538. On March 6, 1971, Train No. 10 departing Denver had UP 944, 1409 and 958 as power, along with baggage 6312, coach 5494, sleeper 1408, coach 5504, lounge-dormitory 6103, and lunch counter-lounge 5007. (Art Gibson email to UP Modelers Yahoo group, February 18, 2007)

A set of four SDP35s were used on the Old Timers special across southern Idaho in September 1973 for the annual Old Timers convention in Boise. Joel Slagg shared photos of the train on Medbury Hill, and in Boise. (Joel Slagg, posted to, April 15, 2023)

In the same email exchange, Bob Yarger wrote that he had seen SDP35s on the City of Denver passing through LaSalle, Colorado, in the summer of 1969. (Bob Yarger email to UP Modelers Yahoo group, February 18, 2007)

In later years, the SDP35s were assigned to pilot duty between Fremont and North Platte, Nebraska, providing UP radios and Coded Cab Signal equipment on run-through Chicago & North Western trains. With the availability of six GP40X units for use on special moves, beginning in mid-1980, the SDP35s were stored, along with hundreds of other examples of UP motive power, due to a downturn in the national economy. They remained in storage until their retirement and sale in 1985.


After taking delivery of high-horsepower double-engined locomotives during the 1963-1965 period, Union Pacific was ready to upgrade other units in its fleet. The road was operating several run-through trains that pooled motive power with other railroads. In 1966, in part to support its pool-power agreements, UP bought off-the-shelf examples of locomotives from all three builders, Electro-Motive, General Electric, and Alco, in the form of EMD's SD40s, GE's U28Cs, and Alco's C-630. Given the costs of owning more units, and confirming previous experience with EMD designs, UP found that the SD40 model was much less costly to both operate and maintain, and placed a follow-on order that brought the SD40 fleet size up to a total of 83 units, while the 10-unit fleets of U28Cs and C-630s remained as orphans--that is, solitary examples of those models on UP. EMD's SD40 employed the builder's newest technology--the 645 model diesel engine, the AR10 alternator, and the D77 traction motor--and UP soon came to appreciate the reduced costs of owning and operating this six-axle, 3,000-horsepower unit over the those of the builder's previous combination of a 567 model engine and DC generator.

UP's first 40 SD40s, numbered 3000-3039, were delivered in March and April 1966. Alco's C-630s were delivered in May and October 1966, and the GE U28Cs were delivered in June and August 1966. More SD40s arrived from October to December 1966, numbered 3048-3082.

After UP acquired its first 83 SD40s in 1966, the road bought SD45s in 1968, and double-engined DDA40Xs and U50Cs in 1969-1971. These high-horsepower units were intended to operate over most of UP's system, from the North Platte terminal in the east to the West Coast terminals. By early 1971, UP was seeing an increasing number of run-through trains with connecting carriers, all of which included agreements for run-through motive power. UP's double-diesel, high-horsepower units were unwelcome on these other roads, so to keep a reliable fleet of power that could be used acceptably on run-through trains, the road returned to EMD for 40 more six-axle, 3,000-horsepower SD40 units. Numbered 3083-3122, they were delivered from August to October 1971, bringing the railroad's SD40 fleet size to 123 units. UP ordered 50 more SD40s for 1972 delivery, but with EMD's change to its "Dash 2" line in January 1972, these were delivered as SD40-2s, numbered 3123-3172.

EMD SD40 Demonstrators

After announcing its "40-Line" in June 1965, EMD completed nine combination test and demonstration units, using its then-new 645-cubic-inch-per-cylinder diesel engine and then-new AR10 alternator, mounted on the frame of the builder's production SD35 locomotive. The first unit, EMD 434, was painted first in EMD demonstrator colors, then in Santa Fe-like blue and yellow. It was later sold to Gulf, Mobile & Ohio and numbered 950 on that road. EMD completed eight others and numbered them 434A to 434H, painting them in an all-black scheme, from which stemmed their "Black Bird" nickname. Known as either SD40Xs or as SDX40s, depending on the source, the units operated in test and demonstration service on several roads, including in Mexico and Canada, before EMD sold them to Union Pacific in February 1966 as UP 3040-3047. In mid-February 1966, 434C and 434D were sent to demonstrate in Canada (as CP 7001 and 7000, respectively), and then to Mexico in March. Six units (434A-B and 434E-H) were delivered to UP immediately, arriving two months before the road's first 40 regular-production SD40s, road numbers 3000-3039. The remaining two units (434C and 434D) were delivered to UP in April 1966 after their tours of Canada and Mexico. Later research has shown that EMD's own electrical schematics has these unique units labeled as SD40X.

The carbodies of units 3040-3045 (six units) had flared radiator sections, similar to those of production SD45s, but shorter. UP 3046 and 3047 had flat radiator sections, like those of production SD35s and SD40s, and were similar in appearance to SD35s, except for having three rooftop 48-inch radiator fans instead of two 48-inch fans bracketing a single 36-inch fan.

Because of their different electrical systems, UP usually kept these eight units together. In January 1974, UP assigned them briefly to potash trains at Soda Springs, Idaho. Within a month, the road reassigned them to the taconite unit ore trains between a mine in Wyoming and the U.S. Steel Corp. steel mill at Geneva, Utah, replacing eight unit sets of SD24s and SD24Bs which had been assigned to that particular service since 1971. In late 1975, UP equipped all eight units with Pacesetter speed control and transferred them to heavy switching and hump yard service in North Platte, Nebraska, and Kansas City, Kansas. Although they were equipped for slow speed heavy switching after 1975, the units were still not limited to yard duties. At times individual units would be assigned to road service as required, and continued to be seen at many locations until the mid 1980s. As examples: UP 3042 was seen in Seattle in March 1977, and 3040 was at Seattle in June 1979. After that time, and until their retirement, or lease to Mexico in 1989, they were used almost solely in heavy switching at North Platte.

Canceled SD40 Order

In early 1967, UP ordered five additional SD40 units. At EMD , they were assigned builder's numbers 32435-32439, and were to carry UP road numbers 3083-3087. UP canceled the order before they were built. The builder's numbers were never used again by EMD for any other units.

GE U28Cs

Union Pacific's 10 U28Cs came in two orders, delivered as UP 2800-2809 in June and September 1966. That same year, UP also bought 10 Alco Century 630s (also known C-630s). The railroad acquired both of these models to compare their cost and performance against the preferred EMD SD40.

UP was apparently unimpressed with the U28C, since no follow-on order materialized. Assigned to the systemwide general pool, the units by the early 1970s were downgraded to secondary freight service, and worked out their last years on the humps at Pocatello, Idaho, and North Platte, Nebraska. All were retired in 1979-1981, with 2804 being stripped and prepared for use as a traveling training locomotive for the road's mechanical department. GE's later-model U30Cs, built for UP six years later, were more successful on UP.

ALCO C-630s

After their delivery in 1966, UP was equally unimpressed with the Alco C-630. These 10 units arrived at a time that UP had only a few Alco switchers, and no remaining Alco road units, and these newer units became mechanical outcasts. They were used on secondary freights, and in 1972 five of the ten units were assigned to service at the road's Pocatello and North Platte hump yards, with the remaining five units still in road service between North Platte and Council Bluffs. They were retired in November 1973 and sold to Duluth, Missabe & Iron Range.

As of August 31, 1968, the official assignments for the 2900s were:

Bill Marvel wrote on December 5, 2015:

In the early 1960s looking to replace first-generation diesels, the road ordered 3000-hp models from Alco, EMD, and GE. Alco’s Century 630 was easily the most powerful with the tractive effort of a Challenger, but at 200 tons it was also the heaviest. Three C630s could walk away with almost anything in the yard, but they were hell on track, and UP needed speed as well as pulling power. The railroad bought dozens of GE U30s and even more EMD SD40s, but kept its ten Centuries for less than a decade before selling them to a Canadian mining road. One remains today, on exhibit in the Arkansas Railroad Museum in Pine Bluff.


While other western roads bought the SD40 model's big brother, the SD45, right after it was first offered in 1966, the always-conservative Union Pacific held back, letting other roads test the new 20-cylinder, 3,600-horsepower engine. After two years, UP remained hopeful of the builder's capabilities, and as a test of EMD's new high-horsepower offering, bought 50 SD45s in two separate orders, plus two single-unit orders. The 50 units were delivered in March and April 1968 for service on the road's high-speed intermodal trains, as evidenced by their high-speed (90 mph) 59:18 gear ratio. Some units were soon regeared for coal and iron-ore traffic, using the more standard 65 mph, 62:15 gear ratio. The units' assignment to high-speed service cooled after the DDA40X Centennial units arrived in 1969-1971, and by mid-1976, all of the SD45s not assigned to unit coal trains were converted to 62:15 gearing, and used on normal manifest trains.

During mid-1968, UP equipped 12 of its SD45s (UP 3638-3649) with lower gear ratios for unit coal train service between Utah and California, operating on what were called the "K Trains," named after Kaiser Steel, for whom the trains were operated. These 12 units were operated in conjunction with six D&RGW SD45s, until the mine in Utah closed in 1983.

In all, 37 SD45s were equipped with radio control, operating in pairs--19 even-numbered units, 3600-3636, were master units, and 18 odd-numbered units, 3601-3635, were remote units. The program was planned from the beginning, with 3622 and 3623 being purchased already specially prepared for installation of radio control equipment. By late 1969, 10 units had been modified for radio-controlled operation. Between late 1969 and late 1972, after the delivery of new DDA40X Centennial locomotives for the road's fast intermodal trains, and the beginning of the arrival of large numbers of SD40-2s, UP equipped all of the SD45s in the 3600-3636 group for radio control. By early 1981, radio-control operations had been used on the Wasatch grade in Utah, in the Blue Mountains in northeast Oregon, and between Salt Lake City and Los Angeles.

UP's SD45s were built as heavier locomotives. During the wreck repairs of three SD45s at UP's Salt Lake City shops in July 1973, which included the removal of the damaged end sheets, it was found that they had two-inch thick frame bottom plates, along with big blocks of steel in the ends between the frame members. By measuring these solid steel blocks, and it was calculated that each block was 300 pounds, and there were three at each end, inside the frame. Also, the end sheets themselves were two inches thick, compared to the 3/4-inch thickness for most locomotives.

UP planned to place additional orders for 60 SD45s for 1971, and 60 more for 1972, but the uncertain reliability of their 20-cylinder engines soon made the road rethink these plans. The need for additional units for manifest service, along with units that could be part of run-through power pools with other roads, was filled by 40 more SD40s in 1971, and by the first of a large fleet of SD40-2s in 1972.

Originally, UP had numbered its SD45s in the 3600-3649 series, but with so many SD40-2s in delivery by 1978, it became apparent that the road numbers of the SD45s would soon be conflicting with the growing numbers of SD40-2s. Beginning in September 1978, and continuing to March 1979, UP renumbered its 50 SD45s to road numbers 1-50. To simplify the renumbering process, the last two digits were retained. As examples of this renumbering, locomotive 3614 became 14 and 3638 became 38. UP 3600 was renumbered to 50.

With a severe downturn in traffic that came with a recession in mid-1980, and due to the units' high-maintenance 20-cylinder engine, UP stored all of its SD45s by late 1982, with at least 40 of them being stored at Yermo, California.

(Read more about Union Pacific's SD45 locomotives)


During early 1968, in its continuing search for improved locomotive designs, UP completed a rebuild project on a single locomotive meant as a precursor to a much larger program. With a total fleet of 79 SD24s (34 SD24s and 45 SD24Bs), UP was looking to bring the SD24 fleet up to current SD40 standards, without having to purchase the newer design. UP SD24 number 423 was rebuilt to SD24M number 3100 in August 1968 using as many upgraded features as was seen as necessary to make the SD24s comparable to the more modern EMD SD40, along with other features not available from builder.

A major feature of the rebuilding effort was the installation of a constant-speed version of the EMD 16 cylinder 645E3 3,000-horsepower engine, upgraded to 3,300 horsepower. As originally installed, the new engine ran at a constant speed, with the locomotive power being varied by changing the level of excitation on the unit's generator. The traction motors were also connected permanently in parallel, with transition being performed by the locomotive's control circuitry. The unit also included variable dynamic braking. These three features were an attempt to copy on a diesel-electric locomotive similar features that had been so successful on the road's earlier 51-75 small gas turbine units 15 years before. The dynamic braking module was purchased from General Electric and was identical to the design used on the U50s built for UP in 1963. The rebuilt unit also used the central engine air intake Dynavanes from a GP35. These last two features forced the air reservoirs from the roof down to under the walkway on the fireman's side.

UP 3100 was the first unit on UP to have the capability of a self-load test, rather than being connected to an external load box. This self load feature was later delivered on UP's DDA40Xs, and on almost all production units from EMD after 1971. In an effort to reduce overall weight, the rebuilt unit also featured fiberglass hood doors, and magnetic door latches. The finished unit weighed in at 399,000 pounds, 13,000 pounds heavier than a standard SD24 at 386,000 pounds.

After less than two years, due to higher fuel consumption and crew complaints, the constant-speed engine was changed to a normal design (reduced to 3,000 horsepower), and the always-in-parallel traction motors were set up in the more normal fashion. The unit became functionally similar to a standard SD40. In 1974, the unit received a thorough rebuilding at the Salt Lake City shops, receiving a rebuilt engine, a rebuilt traction alternator, and was one of the first units to be modified with electric cab heating. At the same time, the magnetic door latches were replaced by regular EMD door latches.

The unit was completed as UP 3100 in 1968. With the planned purchase of additional SD40s, in 1970 it was renumbered to UP 3200, and to UP 3399 in 1972, keeping it from conflicting with the road's new SD40-2s. In 1976, as the SD40-2 fleet continued to grow, the SD24M was renumbered to 3999, and in 1978 it was renumbered to 99. After operating in secondary road service for several years, in 1975, it was assigned to heavy switching service in North Platte, Nebraska, and later in Kansas City.

EMD DDA40X Centennials

During the spring of 1968, after the delivery of the SD45s, UP found that it was again in need of high-horsepower locomotives for its systemwide freight service. By that time, EMD was working on an improvement to its 40-Line, introduced in 1966. So when UP approached EMD with its specifications for an improved DD35, the two companies were able to begin work right away on an upgraded locomotive design. Over the next 13 months, UP and EMD design engineers developed what was to become the largest and most powerful diesel locomotive ever built, the 6900-class "Centennial." The name came from the locomotive being placed in service during the same year (1969) that Union Pacific celebrated the 100th anniversary of the completion of the transcontinental railroad in 1869.

The Centennial design stemmed from UP's interest in developing an improved high-horsepower locomotive that would be as maintenance-free as possible, while still operating with the maximum horsepower attainable. Designated the DDA40X, the model was built with two new-design 3,300-horsepower 645E3A engines, each connected to a new-design AR12 alternator. These two major components replaced EMD's then-standard 3,000-horsepower 645E3 and AR10 combination. To enhance the maintenance-free concept, the electrical controls were replaced with solid-state electronic modules that would allow replacement in the field, allowing any locomotive with a failure to be returned to service without the downtime from having to troubleshoot the failure. With replaceable components, the troubleshooting could take place back at the shop, rather than out on the road. The traction motors were also of a new design, with all eight motors wired in parallel at all times, and transition taking place in the electronic control system. The Centennials were also equipped with a unique self-load testing feature that used the units' dynamic braking grids, allowing the unit to be load-tested away from a stationary load box. (Up to that time, many load boxes were located near large shops and were usually made from dynamic braking grids removed from retired locomotives. Others, such as those at the Salt Lake City shops, were purpose-built by vendors as load boxes.) The air brake components were also of a reduced-maintenance design, being mounted on a replaceable pallet situated under the locomotive cab. All of these features would turn up in January 1972 as major components of EMD's new Dash-2 line of locomotives.

The first 6900-series unit was completed as a special effort to ensure its completion in time for the centennial Golden Spike celebration at Promontory, Utah, on May 10, 1969. The locomotive was delivered to UP in late April 1969, and pulled the Golden Spike Centennial Limited special from Kansas City, Missouri, to Ogden, Utah. The initial order was for 25 units, numbered 6900-6924. Before the first order was completed, UP ordered 22 more units, bringing the fleet size up to 47 units, the highest-numbered locomotive being UP 6946, which was delivered in September 1971.

Between 1970 and 1980, the Centennials ruled Union Pacific's main lines between Nebraska and the West Coast. Because of the high-mileage service of the 6900 fleet (many units already had accumulated 1 million miles), UP initiated a "Fail-Free" program in March 1976, to be carried out by shop forces at Omaha. As each locomotive went through the program, it got reconditioned electrical components, main generators, engines, and traction motors. The program was completed in April 1977, but with these units seeing an average monthly usage of 22,000 miles, UP started another "Fail-Free" program in late 1978.

After a decade of high mileage on the road's most important trains, and due to the high maintenance costs of their special mechanical and electrical components, the fleet became among the earliest classes of units to be stored during the severe business downturn of 1980. Twenty-five units were stored at Council Bluffs, Iowa, in May 1980, with another 12 units stored at North Platte, Nebraska, and the remainder of the class being stored at Salt Lake City (6903 and 6921 had been wrecked earlier). The 37 units at Council Bluffs and North Platte were gathered at Las Vegas, Nevada, in early October 1980. The entire class (37 units at Las Vegas and eight units at Salt Lake City) was moved to Yermo, California, during January and February 1982, where they remained for well over 1,000 days.

(Read more about Union Pacific's DDA40X Centennial locomotives)

GE U50Cs

Union Pacific's 40 U50Cs were delivered from November 1969 to November 1971. Numbered 5000-5039, they were built using trade-in trucks from UP's 30 8,500-horsepower gas-turbine-electric locomotives. The design of the U50C was fashioned in response to UP's requirement for a high-horsepower locomotive for the road's high-speed systemwide freight trains. It was the same specification that had brought about the development of the 6900-class Centennial units during the same period.

General Electric took the earlier design of its U50 locomotive, delivered to UP between October 1963 and August 1965, and made several changes. The original U50s essentially were composed of two of the builder's U25B locomotives on a common frame, using two of GE's 2,500-horsepower FDL diesel engines. Instead of the four-axle truck used by EMD for its comparable DD35, GE made use of the twin two-axle trucks connected by span bolsters from retired 4500 GTE gas turbines. For this new design, GE found that the need was for speed rather than pulling power, so six-axle trucks from retired 8500 GTE gas turbines were used. Also, the previous model's 16-cylinder engines were replaced by shorter 12-cylinder engines that produced the same combined 5,000 horsepower. The two engines were reversed in their placement from the configuration of the earlier model, putting their radiator sections at the center of the locomotive. The shorter overall unit length forced adoption of an overhanging design of radiator that GE had used on its U33-series locomotives. The earlier U50 had been built without a nose door, which did not allow crew access to or from a front-coupled unit. GE followed the same design for the first 12 U50Cs, but crew complaints brought a nose door to the later units, and the first 12 units were retrofitted by the road's Omaha shops with nose doors.

In a test that was meant to provide some final engineering data prior to actual delivery of the U50Cs, UP U25B 632 in April 1969 was modified with the new 12-cylinder engine, replacing its original 16-cylinder engine. The unit was operated in stationary tests, and in limited road service, gathering the needed data for some final adjustments to the new engine's design. The test engine was removed by the end of 1969.

UP 5000 and 5001 were first operated in gray primer paint for several weeks prior to delivery to their owner; 5000 operated on GE's Erie, Pa., test track, and 5001 operated in road service on the Erie Lackawanna. Both units were rushed to completion, leaving the GE factory in October and November 1969, just prior to a lengthy strike at GE, which lasted until March 1970. Unit 5000 was delivered on November 21, 1969, and 5001 was delivered on October 31, 1969. The remainder of the first order, 5002-5019, was finished starting in March 1970, with 5002 being delivered on April 6, and the others following on a regular schedule thereafter, with 5019 arriving in February 1971. The second order, for units 5020-5039, was delivered between May and November 1971.

The U50C was designed at the request of D. S. Neuhart, Union Pacific's General Superintendent of Motive Power & Machinery, a title that is today known as Chief Mechanical Officer. There were rumors about the forced design features desired by Neuhart.

Don Strack wrote in December 2015:

During a special maintenance class for the newest GE U30C locomotives, there were informal stories that told about the problems with the U50C, and what Neuhart wanted from GE in the design of the locomotive. Against its better judgment, GE was pushed for many of the design features, and was somewhat vindicated after the U50C was such a massive failure after just seven years. I had a history class while in college, in which the professor mentioned several times that it is the personalities that drive history. I can certainly see that in the history of UP's motive power, all the way back to the 1870s. (Don Strack was a journeyman mechanic for Union Pacific from 1969 to 1979.)

(Read more about the men who ran UP's mechanical department)

According to Union Pacific records, the U50Cs suffered from chronic low oil pressure problems, along with water leaks and excessive dynamic braking grid failures. Other sources have stated that the U50Cs suffered from overheating of the high-voltage (600-volt D.C.) cabling, which was made of aluminum to save on overall weight. Early in 1975, UP 5012 was the victim of a major high-voltage electrical fire that was the worst of several that plagued the U50Cs. To alleviate the problem, UP considered having a contractor, such as Morrison-Knudsen in Boise, Idaho, completely rewire the units, using more dependable copper cabling, which UP itself had already done to one unit at Salt Lake City. Rewiring was found to be too costly, considering all of the other mechanical problems from which the design suffered, including cracked truck frames, which had come from retired gas turbine locomotives.

With a business downturn in 1976, the operating career of the U50Cs ended and they were the first to be placed into storage, with 22 units being stored at North Platte, Nebraska. Others soon followed, and, by the end of 1976, all of the U50Cs were in storage, with the 18 units at North Platte kept in stored-serviceable status. The remaining 22 units were stored unserviceable at Council Bluffs, Iowa.

While no 5000-class units ever operated in road service again, UP in early 1978 put five of them (5017, 5019, 5026, 5027, and 5039) back into operating condition and, due to a coal miners strike, leased them as stationary 3,700-kilowatt electrical power plants. The first four went to Ford Motor Co. for use at its Hazelwood, Missouri, and Lorain, Ohio, assembly plants, and the last one, UP 5039, was used by FMC at its Chain Link Division plant in Indianapolis. Others were readied for similar service, but the coal strike ended before they could be leased out. The five units that had been leased were soon returned to the storage line at Council Bluffs.

All 40 units were officially removed from service in mid-1976, after just five to seven years of operational road freight service, the shortest-lived of any of Union Pacific's mainline road units. Some units operated even less, having been permanently sidelined in late 1974, only three years after being built. UP 5000-5016 were retired in March 1977; UP 5017-5039 were retired in February 1978. All were sold to a Kansas City scrapper, Erman Corp., in May and August 1977, and in June 1978.

EMD SD40-2s

By early 1971, UP's two most recent designs for high-horsepower, double-diesel locomotives, the 6900-series Centennials and the 5000-series U50Cs, were filling the road's need for high-speed freight motive power. But UP needed motive power for another regular assignment. During the late 1960s, UP and its connecting roads began cooperating to move run-through trains, with blocks of cars that had been assembled for their final destination prearranged in groupings that did not need to be broken apart and reclassified every time they moved from one railroad to the next. These run-through trains also included agreements for UP and the others to pool their motive power to prevent having to change locomotives as the trains were interchanged between the participating railroads.

The other roads did not have the capability or desire to operate UP's large double-diesel locomotives, and UP usually furnished its 1966-built SD40s, along with other models that were standard on the other roads. By early 1971, run-through traffic had grown, and UP was also beginning to operate more unit coal trains. The road needed more SD40s, a model with 3,000 horsepower and six axles that was becoming a standard nationwide for most larger railroads. Forty new SD40s were delivered from August to October 1971, numbered UP 3083-3122. UP ordered more SD40s for delivery in 1972, but EMD notified the road that it would be changing its line of five domestic locomotive models, beginning on January 1, 1972, using more than 50 design improvements, and as a result, the manufacturer would deliver the units in the form of the successor model, the SD40-2.

For improved maintenance, all of EMD's new models would feature an improved electrical control system of solid-state electronic modules, a concept first used on UP's Centennial units three years before. Although it did not generate higher horsepower than its predecessor, the diesel engine contained features that greatly improved its reliability. On the SD40-2, and all other six-axle units, the design of the trucks was changed to improve traction, and to better control wheel slip. UP's first SD40-2s (50 units numbered 3123-3172) were some of the first of the new model built (10 units for Kansas City Southern were the first), and were delivered in January and February 1972.

In September 1971, D. S. Neuhart retired after serving as the head of UP's Motive Power & Machinery Department since 1949. He was responsible for many of UP's trademark locomotives, notably the gas-turbines and all of the double-diesels of both 1963-1965 and 1969-1971. Studies of the road's motive power requirements commissioned by Neuhart had shown that per-unit costs remained the same, no matter how much horsepower a unit produced. Armed with that finding, Neuhart crafted a solution to UP's power needs that revolved around large, high-horsepower, single-unit locomotives.

Neuhart's successor was F. D. Accord, who believed that UP should completely modernize its diesel fleet with a few standard models. The timing of the change at the top matched well with EMD's changeover in production from the SD40 to the SD40-2 (along with continued availability of GE's counterpart model, the U30C). UP began purchasing SD40-2s and, over the next eight years, EMD delivered a total of 686 units of that model, including 65 units with modifications for high-speed service. The standard SD40-2s were delivered between January 1972 and November 1980, numbered from 3123 to 3808, and the high-speed units were delivered between July 1976 and August 1979. During the same eight-year span, UP also received 150 U30Cs (April 1972-October 1976) and 140 C30-7s (the replacement for the U30C, July 1977-October 1980).

Soon the SD40-2s were put to work systemwide on all of the road's mainline trains. The term ubiquitous is truly appropriate, because these locomotives quickly filtered everywhere throughout the system. Their arrival allowed UP to retire almost all of its odd-ball and one-of-a -kind locomotives, along with most of the older designs that had served the company so well since the 1950s. The largest group of units to be replaced were the GP9s, both as cab units and as booster units. By this time, most of the SD24 cab units had gravitated to useful second careers as switching service, but their matching booster units, known as SD24Bs, were suited strictly for mainline service, and UP retired them. The U50C units had proven to be a costly mistake, and the availability of new SD40-2s, U30Cs, and C30-7s allowed these troublesome units to be retired. UP had purchased its earlier trademark double-diesels in 1963-1965. These, too, were retired in order to minimize the variety of locomotives that needed to be maintained.

The run-through trains were using more and more of UP's new SD40-2s, which were turning up at the engine servicing terminals of all of the nation's other railroads. In 1977, the operation of UP SD40-2s began on the previously all-Alco Utah Railway, with three SD40-2s forming UP's contribution to the successful start-up of a new unit coal train. There was also pooling of motive power across the border with Canada. Twenty UP SD40-2s were modified for service in Canada, as UP and Canadian Pacific initiated a new pool train in early 1979. Modifications for Canadian service included the installation of ditch lights on locomotives 3396-3414.

Throughout the production period of UP's SD40-2 fleet, EMD continued to make small improvements. Some of these changes were apparent in the exterior appearance of new SD40-2s. UP also made changes in some of the components supplied as part of new deliveries. After 165 units, the design of the handbrake was changed from a lever ratchet to a wheel. After 182 units, the style of the screen over the radiator shutters was changed from an open grid design to a corrugated screen to better control duct and debris that clogged the radiators, thus preventing overheating.

Possibly the most notable change was in the low nose ahead of the locomotives' cab. The first 120 units were delivered with EMD's standard 81-inch nose. With the prospect of increasing remote-control operations, and to quell possible complaints for enhanced crew collision protection, UP specified that the next 246 units be delivered with a longer (116-inch) low nose. The last 320 units, from 3489 to 3808, were delivered with EMD's updated standard nose that was 88 inches long.

Another group of external changes were prompted by efforts to reduce noise. The Noise Control Act of 1972 gave the federal Environmental Protection Agency authority to control noise emissions on the nation's railroads. During 1974, EPA began investigating the sources of railroad noise pollution, working with the carriers to develop reasonable standards to reduce noise. In January 1980, EPA published its noise-control standards. In anticipation of this, the railroads and the locomotive builders had begun development work to reduce the sources of locomotive noise. On the SD40-2 locomotives ordered by UP for 1980 delivery, noise reduction features included redesigned radiator fans (called Q-fans, for quiet fans) and silencers on the units' exhaust stacks. UP 3659-3768, a 110-unit order delivered from January to March 1980, were the first units on UP (along with C30-7s 2460-2499, delivered in January and February 1980), to be equipped with noise reduction features.

SD40-2S Units

UP 3805-3808 were built as test units and were equipped with a improved engines and turbochargers, longer radiators, two-speed radiator fans, as a test for EMD to increase cooling capacity for its SD40-2 model. At the conclusion of the one-year test, all four units were equipped with standard engines and standard turbochargers.

The carbodies were longer than a standard SD40-2 by approximately 28 inches to accommodate longer radiators; each long-hood is fitted with eight doors under radiator section, rather than the seven doors seen on a standard SD40-2, as well as a shorter rear platform.

These units have previously been reported as being equipped with improved wheel-slip control (a feature of the later Super Series units). Research in the railroad's mechanical department records completed during 2000 found that these units were not equipped with the Super Series improved wheel slip control features.

(Read more about these four unique UP SD40-2 locomotives)

Canceled 1975 order for SD40-2 B-units

Under Work Order 11442, dated November 4, 1974, UP ordered 23 SD40-2 B-units from EMD. Fifteen units were to be delivered in May 1975 and eight units in June 1975, at a cost of $387,000 per unit, compared to $412,000 for a normal cab-equipped SD40-2. The units were to be equipped with all of the standard features for a UP SD40-2 and were to be numbered 3288B-3310B. (Letter, F. D. Acord to E. C. Beig and others, including all top-level management in MP&M Department)

The proposed group of 23 locomotives was to be assigned to high-speed systemwide service, spliced between pairs of the road's 6900-class Centennial units, making a 16,200-horsepower motive power set that could operate over UP's western mainline. We'll never know what a factory-built SD40-2 B-unit would have looked like; UP canceled the order in February 1975 after deciding to modify SD40-2s for high-speed service. Without documentation, we can only guess that possibly the lack of flexibility of a cabless booster in operational situations may have weighed against the idea. (part from The Mixed Train, February 1975, page 8; CTC Board, Issue 151/152, April 1975, page 10)

In his research of EMD builder records, Bob Lehmuth found the same group of 23 locomotives. EMD records show that the locomotives were assigned order 74682, and were to be numbered as UP 3123B to 3145B. (Bob Lehmuth, email dated June 11, 2017)

8000-class SD40-2Hs and SD40-2Ms

Beginning in February 1976 UP started to modify SD40-2s 3240-3274 for 80 mph operation, using the same 59:18 gearing as the road's 6900-class Centennial units, along with changes in the electrical controls to allow the units to be used in high-speed service. The modifications were completed and all 35 units were in high-speed service by July 1976. Three later orders for UP SD40-2s were delivered with the high-speed modifications: UP 3305-3334 were delivered as UP 8035-8064 in July 1976; UP 3400-3409 were delivered as UP 8065-8074 in May 1977; and UP 3584-3608 were delivered as UP 8075-8099 in July and August 1979. These 100 8000-class high-speed SD40-2s were most often seen as one or two units spliced between two 6900-class DDA40Xs on the railroad's hottest trains, which operated between North Platte, Nebraska, and the West Coast.

The program came to an end in June 1980 because of operational problems associated with keeping a particular class of locomotives assigned to a single type of service, along with the extra costs of special spare parts and maintenance; the reasoning was similar to that which caused cabless booster units to fall from favor 20 years earlier. In early June 1980, the railroad began modifying the units back to standard SD40-2s, and renumbering them either to their previous numbers, or into slots in the 3000 series that were left blank as other SD40-2s were being delivered. The program was briefly put on hold in late August 1980 with an increase in high-speed traffic that wouldn't allow the units to be shopped for the modifications (all of the Centennials had been stored, and more SD40-2s were needed to take their place). The program of returning the 8000s back to normal SD40-2s resumed in April 1981, and was completed in early March 1982.

GE U30Cs

Although the 10 U28Cs were not successful on UP, six years later, the road ordered 20 of the builder's newest equivalent model, the U30C, which had replaced the U28C model. Between April 1972 and October 1976, UP took delivery of a total of 150 U30Cs, showing that the builder had indeed made improvements.

The first 20 U30Cs arrived at the same time as UP's first SD40-2s, from April to June 1972, numbered 2810-2829, following the 10 U28Cs. Like the SD40-2s, the U30Cs impressed UP right away, and the road began buying them on a continuing basis. Thirty more came between February and June 1973, numbered 2830-2869; 35 were delivered from March to July 1974, numbered 2870-2904; and 15 came from April to July 1975, numbered 2905-2919. The final group of 40 units was delivered between July and October 1976, numbered 2920-2959.

UP 2915-2919 were delivered new from GE in June and July 1975 and were equipped with 7FCL-16A1 engines, which had their 16 cylinder diesel engines configured with 14 power cylinders and two cylinders functioning as air compressors, a practice common in stationary power plants. All five units had their engines replaced with standard 7FDL-16E18 16-cylinder engines during 1977 and 1978. The project it was a GE test, and GE supplied the replacement engines, and reimbursed UP for the cost of the engine swaps in the Salt Lake shops, which were done under GE supervision.

Like the SD40-2s, the U30Cs were first assigned to general pool service. But by late 1978, the units began to excel in heavy-haul unit train service, and UP equipped them with Pacesetter speed control to assure consistent slow speeds during coal train loading and unloading. Also like the SD40-2s, throughout the 1970s and 1980s, UP began to rely on GE's 3,000-horsepower, six-axle unit as a jack-of-all-trades locomotive to serve in a make-up role on all types of service systemwide, but they were mainly used on coal trains in southern Wyoming.

GE C30-7s

Just as the SD40-2 was a great improvement over the SD40, General Electric's C30-7 proved to be a much more reliable version of the earlier U30C. As a result, UP placed orders for new units from both builders on a continuous, year-to-year basis. The newest U30Cs were delivered to UP in October 1976. The follow-on order for new GE units came as C30-7s, less than a year later, in July 1977. By the time the newest units were delivered, in October 1980, Union Pacific was operating 140 C30-7s. The C30-7 fleet was delivered over a three-year period between July 1977 and October 1980. Like the U30Cs before them, all were equipped with Pacesetter lead controls for use in low-speed unit train loading at various south-central and western Wyoming coal mines.

The C30-7 model included several internal and external improvements over the U30C, with some improvements being apparent by changes in the carbody. Most noticeable was an added "step" in the carbody to accommodate a relocated oil filter and oil cooler. The first order of 15 C30-7s, 2960-2974, was delivered from July to September 1977, and they were numbered in sequence behind UP's newest U30Cs. The last five units in this group were equipped with a much different diesel engine. In a test, the five units, although equipped with 16-cylinder engines, were rated at 3,000 horsepower on just 14 cylinders. The two remaining cylinders were configured to operate as air compressors. The test lasted only a year, and the units were converted back to their standard configuration.

The first order of C30-7s proved to be satisfactory performers in both the general motive power pool and in dedicated unit-train coal service, so UP soon placed a second order. This order was to be for 15 units, and a third order for 30 units followed close behind. This projected additional 45 units would obviously fill up the remaining road number slots in the 2900-series numbers, and conflict with the numbers for the 1966-built SD40s in the 3000-series. To remedy this potential conflict, UP renumbered the first 15 units to a new 2400-series number group, as 2400-2414, between April and July 1978. The second order was delivered in June and July 1978 as 2415-2429, and the third order was delivered in December 1978 and January 1979 as 2430-2459.

The next group of C30-7s for UP, 2460-2499, 40 units delivered in January and February 1980, comprised the first units on the railroad (along with SD40-2s 3659-3768, 110 units delivered between January and March 1980) to be equipped with noise reduction features. These modifications brought the railroad into compliance with standards published by EPA in January 1980. On these GE units, the most obvious feature was a much larger exhaust stack.

A fifth and final order of C30-7s for UP arrived between August and October 1980, numbered 2500-2539. A design feature of these units was the lack of fixed cab side windows adjacent to the sliding windows. A new federal regulation that took effect on January 1, 1980, required the use of projectile-resistant laminated glazing in all locomotive and caboose windows. This grade of glass is much more expensive than standard glass, and to save both initial installation costs, and replacement costs later on, UP (and other railroads) eliminated these extra windows. These last 40 units are also unique as being some of the last units to enter service in the lettering scheme that used 20-inch numbers on the hood-side of the units. Less than one month after the last C30-7, 2539, was placed into service, UP began using a new lettering scheme that moved the 20-inch unit numbers from the hood sides to the sides of the unit cabs, right below the windows.

Units in storage

During downturns in traffic, UP, like many other railroads, has always stored surplus locomotives. Possibly the most famous was the storage of large numbers of steam road locomotives during the late 1950s, and their seasonal reactivation to help the now-dominant diesels handle the fall rush of business. This continued for a significant four-year period, ending only in 1959 with the delivery of 30 SD24 cab units and 45 SD24 booster units.

There have, of course, been times when a portion of the diesel fleet also has been stored. One of the first times came in the recession of 1962-1964, when large numbers of Alco freight and passenger units operating in Kansas and Nebraska were stored. Some were leased out to other railroads to help them with their own seasonal rushes, which usually fell at different times than those of UP's own rushes.

During September and October 1972, UP stored 19 GP9 boosters at Ogden, Utah, along with another 14 boosters at Portland's Albina yard. The traffic slump continued, and with new SD40-2s readily available, by August and September 1974, there were as many as 110 GP9 and SD24 booster units stored at Albina, at Cheyenne, Wyoming, and at Denver. By July 1975, the quantity of all stored units had risen to 170 units, and now included yard switchers and many DD35 booster units. The slump was common throughout the West, with Santa Fe having 114 units in storage, and SP having 312 units laid up.

Union Pacific continued to modernize its fleet, but traffic levels were still down. From April through July 1975, 20 new GP38-2s, 17 new SD40-2s, and 15 new U30Cs were given acceptance runs between Omaha and North Platte, then placed into storage to avoid having to pay on their equipment trusts, which wouldn't be activated until the units actually entered service. Fifty-eight units were stored at Council Bluffs, Iowa, alone. Business soon improved, and the new units were all in service by March 1976. By the same time, most of the U50C fleet was stored, part of the remaining 71 units in storage, but they were never to return to service. There was an increase to 104 units by July, with 14 of them sitting in Salt Lake City.

By February 1977, 84 units were stored. The storage lines now included all of the DD35 booster units, with these unusual units sitting unused at Omaha, Council Bluffs, North Platte, Salt Lake City, Las Vegas, and Los Angeles. In July, 105 units were in storage, including all of the DD35s, most of the SD24Bs, U50Cs, and DD35 cab units, and varying numbers of each of the older Geeps and switchers.

The 1977 fall season brought a much-needed increase in traffic, and the DD35 cab and booster units all returned to service. Notably, the U50Cs did not return to service, and they were all retired by February 1978. There was still an excess of switcher units, and these remained in storage. By August, business continued to improve, with just 42 units now stored, all being older, first-generation models. The 1978 season was slower than the 1977 season, so the DD35s were returned to storage, where they remained until their retirement in 1979-1981.

Throughout the 1978 and 1979 seasons, business slowed, with 30 to 40 units remaining in dead lines. Then the largest business slump in UP history hit. A sudden rise in interest rates drove the nation's economy into a downward spiral that was to depress UP's traffic levels for another three years. Carloadings began to decline in late April 1980, and UP reacted by storing its most costly locomotives, including many of the 6900-series Centennial units. By late June, 176 units were stored, including the Centennials and several of the newer units, all at Council Bluffs, North Platte, and Cheyenne.

During this same time, UP repossessed the 76 units it had leased to the now-bankrupt Rock Island, and many of these joined the storage lines. By this time, it became apparent that the downturn would stretch for an extended period of time, so many of the stored units were prepared for long-term storage, and moved to the drier climate of Las Vegas, Nevada. Along with the large number of locomotives in storage, UP also had 3,400 cars in storage.

The lines of unserviceable units continued to grow, and by January 1981, UP had stored 338 units, awaiting a return to service. The number increased to 436 units in July, and included all of the Centennials, all of the SDP35s, all of the GP30Bs, 30 of the 50 SD45s, 30 SD40s, 139 SD40-2s, and 102 U30Cs. In late September 1981, to increase storage capacity, UP began to use the yard at Yermo, California. (located in the very dry Mojave desert of southern California), with 37 units being located there by October. By late November, there were 113 units at Yermo, 44 at Las Vegas, 42 at Los Angeles, 51 at Salt Lake City, and 51 at Council Bluffs, with additional units still at Omaha, North Platte, and Cheyenne. By far, the greatest number of stored units were in serviceable condition.

By mid-December 1981, UP had 538 units stored, along with 4,500 cars (2,500 covered hoppers alone) and 100 cabooses. Employees suffered also: 2,500 had been laid off. The average number of days each unit had been stored stood at 212 days, with the ex-Rock Island units and the Centennials being in storage more than 500 days. Two months later, in February 1982, the number of cars stored climbed to 6,250. By May 1982, Union Pacific had 682 units stored. There were 8,495 cars in storage, including 4,036 covered hoppers, 2,083 boxcars, 1,612 open-top hoppers, and 764 mechanical reefers. The railroad's business was off by 38 percent. It was even worse for a competitor, Santa Fe, which registered a 57 percent drop in business volume. During the following month, UP had 718 locomotives stored, in all conditions: serviceable, unserviceable, awaiting retirement, or awaiting repairs. That quantity represented just over 43 percent of UP's total fleet of 1,627 locomotives.

As the level of business seemed to settle at its lowest, during the last six months of 1982, the number of units in storage began to change almost on a daily basis. Serviceable units were removed from storage daily to pull trains as needed. From month to month, the total numbers began to change, with variations in the total of as many as 30 to 50 units. The number and types of stored cars also began to fluctuate as traffic levels stabilized.

As of the end of October 1982, UP had 660 units stored. There were 138 serviceable at Yermo; 175 at North Platte; 138 at Council Bluffs; 61 at Salt Lake City; 37 at Los Angeles; and 17 Kansas City, plus other units stored at Albina, Cheyenne, Hinkle, Pocatello, and Omaha. The average number of days in storage stood at 278 days; the Centennials had been in storage an average of 827 days, and the SDP35s had been stored an average of 863 days. The repossessed Rock Island units had been stored an average of 789 days. UP ended the year with 614 units still in storage.

Yard Slugs

A slug is an unpowered locomotive with only traction motors, that depends on a semi-permanently coupled powered locomotive for its electrical power. The combination is used to increase the pulling tractive effort of the matched set, usually in a yard switching situation. Union Pacific built eight yard slug units, including six from retired GP9Bs and two from retired SD24Bs.

UP's eight yard slugs were used at its three hump yards: North Platte, Nebraska, East Los Angeles, California, and Pocatello, Idaho, although the first slugs were used at the yard complex at North Platte. These first slugs, three four-axle units, numbered as S1, S2 and S3, and rebuilt from retired GP9Bs, were completed in late 1973 and early 1974, and entered service mated with SD7s. UP found that these sets needed more power than what was available from the 1,500-horsepower SD7s, so the three later four-axle slugs, also rebuilt from retired GP9Bs and completed in 1975 and 1976 as S4, S5, and S6, were mated with 2,400-horsepower SD24s. Experience showed that additional axles were needed, so two additional slugs, completed in 1978 as S7 and S8, were rebuilt from retired SD24Bs.

By 1981, operational experience again showed that still more horsepower was needed. During 1981 and 1982, all but S4 and S6 were mated with 3,000-horsepower SD40s. S4 and S6 were mated with SD40s in 1985. By the end of 1982, only S3 was no longer in operation, having been wrecked. It was retired in September 1982.

Electric E-100 and E-101

UP electric locomotive E-100 was built new as Glendale & Montrose Railway 22. The Glendale & Montrose Railway was a nine-mile railroad that operated between Glendale and Montrose, California, serving as the UP connection to the city of Glendale. G&M purchased the electric locomotive in 1923 especially to protect the UP traffic.

G&M went into bankruptcy and its last day of operation was on December 30, 1930. The railroad, and its electric locomotive, were purchased by UP in May 1931, and UP kept the electric locomotive assigned to its original home tracks until the operation was dieselized with a new UP NW2 in July 1942. The E-100 was sent to UP's other electric subsidiary, Yakima Valley Transportation in Yakima, Washington. UP E-100 was equipped with 36-inch wheels and four Westinghouse Model 562-D5, 100-horsepower traction motors. It was UP class B-1.

UP E-101 was the assigned road number for the former G&M 21, but the locomotive was not renumbered. G&M 21 was a 35-ton, 300-horsepower electric locomotive acquired by Union Pacific in May 1931 along with the G&M. The Glendale & Montrose Railway had purchased its number 21 secondhand from Pacific Electric Railway (ex-PE 1537). Pacific Electric Railway built the locomotive in 1903 in its Los Angeles Shops from retired PE flat car 3072.

As originally built, PE 1537 was a flatbed work motor with a center cab. When the Glendale & Montrose Railway purchased the locomotive, it added a much larger body, which covered almost the entire frame, making it a combination box motor and locomotive. After UP purchased G&M, Union Pacific used the 21 only as stand-by for G&M 22, and so far as is known the locomotive never was renumbered to UP E-101. It was stored at the former G&M yard in Glendale and by 1934 was boarded up and out of service.

The former G&M 21 was sold for scrap in 1936 and by September 1936 was in the scrap yard of the Pennsylvania Iron & Steel Co. in Los Angeles. Some sources indicate that the former G&M 21 was finally burned by Pacific Electric at its Torrance Shops. G&M 21 was equipped with 33-inch wheels and four Westinghouse Model 76 75-horsepower traction motors.