The E1 was an early passenger-train diesel locomotive sporting 1800 HP, with an A1A-A1A wheel arrangement, manufactured by Electro-Motive Corporation of La Grange, Illinois. They were built during 1937 and 1938 for the ATSF Railway for a new generation of diesel-powered streamlined trains. Eight cab-equipped lead A-units and three cabless booster B-units were built. The initial three locomotives were AB pairs built to haul the Santa Fe's Super Chief diesel streamliners, while the others were built as single A-units to haul shorter trains. The locomotives were diesel-electrics with two 900 hp (670kW) Winton 201-A engines each, with each engine driving its own generator to power the traction motors. The E1 was the second model in a long line of passenger diesels of similar design known as EMD E-units. All Winton 201A-engined Santa Fe passenger units, including the E1s, were extensively rebuilt into the 80-class E8M engines in 1952-53. These were similar to production E8 models, but reduced to 2000 hp so as not to burn out the early traction (axle) motors (which were reused).