Union Pacific has retained only one of its 47 Centennial diesel-electric locomotives, No. 6936. The Centennials were the largest diesel-electric locomotives ever built. Actually comprising two engines on one frame, they delivered 6,600 horsepower.

It is one of 105 Challengers built for Union Pacific between 1936 and 1943 and was, for many years, the only operating engine of its class in the world – the largest and most powerful operating steam locomotive.

Railroads already are one of the most fuel-efficient means of transportation. Moving freight by rail instead of truck reduces GHG emissions by up to 75%. On average, Union Pacific moves a ton of freight 463 miles on a single gallon of diesel fuel.

Working with them were the "800-class" high-speed passenger locomotives, as well as hundreds of older class steam engines. Union Pacific's steam legacy continues today with the preservation and operation of its historic fleet – No. 844 and No. 4014.

The turbine, rather than an internal combustion diesel engine, drove an alternator/generator to supply electricity to electric motors mounted on the axles. Union Pacific's gas turbine fleet totalled 55 locomotives.

Steam Locomotive No. 844 is the last steam locomotive built for Union Pacific Railroad. It was delivered in 1944. A high-speed passenger engine, it pulled such widely known trains as the Overland Limited, Los Angeles Limited, Portland Rose and Challenger.

The preservation of its fleet speaks to the high value UP places on its heritage and its role in America's history. No other railroad in this country has retained its historical equipment and honored its past like the Union Pacific.

To be notified when news about Union Pacific's legendary steam program (including future steam excursions by Living Legend No. 844 and Big Boy No. 4014) becomes available, join the Official Union Pacific Steam Club at http://UP.com/SteamClub!

Union Pacific has retained only one of its 47 Centennial diesel-electric locomotives, No. 6936. The Centennials were the largest diesel-electric locomotives ever built. Actually comprising two engines on one frame, they delivered 6,600 horsepower.

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