Union Pacific 'Centennials'

The class leader at Omaha, Nebraska, 1969. (UP postcard pic)

"The DDA40X is a 6,600-horsepower (4.92-megawatt) D-D [Do-Do]experimental diesel-electric built by General Motors' EMD division in La Grange, Illinois, for the Union Pacific Railroad. Nicknamed "Centennials" because they were built around the 100th anniversary of the completion of the First Transcontinental Railroad, and "Big Jack", the DDA40X uses two diesel engine prime movers, each rated at 3,300 horsepower (2.46 megawatts).
"The DDA40X is the most powerful single-unit diesel-electric locomotive ever built, surpassing the ALCO Century 855 built in 1964, which was rated at 5,500 hp (4.10 MW). However, more recent designs, such as the EMD SD90MAC and GE AC6000CW, have come close; both of these locomotives were rated at 6,000 hp (4.47 MW). It is also the third-most-powerful internal-combustion locomotive ever built, exceeded by the Russian Railways GT1 and Union Pacific GTEL gas turbine units. [At 98 ft 5 in (30 metres)] it is the longest single-unit diesel locomotive ever built."

A total of 47 were manufactured between April 1969 and September 1971 of which 13 survive today, including No. 6936 which is still in service with UP.

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