Even without yellow paint, the U50C would have been immediately recognizable as Union Pacific power. From its unique 4-12-2 to the Big Boy to its 8500 horsepower gas turbine, no other railroad had such a penchant for huge, larger-than-life locomotives. So it seemed only natural that in 1963, UP Superintendent of Motive Power David Neuhart approached EMD, Alco and GE about building a 5,000 horsepower diesel - twice the horsepower of a typical road diesel of the time. A key impetus was a U.P. study that had indicated diesel maintenance costs were about the same regardless of horsepower.
All three builders responded by mounting two of their standard power plants on one chassis. GE's initial effort was the U50, basically two of its ground-breaking U25B's in one unit, complete with four two-axle trucks. While UP liked the engine well enough to order 26 units, the U50 was extremely heavy and a bit ungainly, with the four-truck arrangement limiting it to lower-speed drag freight service.
GE addressed those issues with the U50C, designed more for power at speed. The new engine rode on a pair of six-wheel trucks recycled from retired 8,500 hp turbines. It had numerous features designed to reduce weight, including 12-cylinder rather than 16-cylinder prime movers that produced the same horsepower; a shorter frame; and aluminum instead of copper wiring. Forty U50Cs were delivered in 1969 - 71. The design changes, however, proved troublesome, especially the aluminum wiring that tended to overheat and catch fire, and a traffic downturn in 1976 led to the fleet's retirement.
Ironically, the U50C was pretty close to what railroads today consider the ideal locomotive: a 4300 - 4400 hp diesel with six-wheel trucks about 75' long. Maybe the UP just figured that out before anybody else.