The EMD FT was a 1,350-horsepower diesel-electric locomotive produced between November 1939, and November 1945, by General Motors' Electro-Motive Division (the "F" stood for 1400 horsepower (rounded from 1350) and the "T" for twin, as it came standard in a two-unit set). All told 555 cab-equipped A units were built, along with 541 cabless booster B units, for a grand total of 1,096 units. The locomotives were all sold to customers in the United States. It was the first model in EMD's very successful F-unit series of cab unit freight diesels, and was the locomotive that convinced many U.S. railroads that the diesel-electric freight locomotive was the future. Many rail historians consider the FT one of the most important locomotive models of all time.
The locomotive was a railway application of propulsion technology developed for United States Navy fleet submarines. Sargo class submarines launched in 1939 used 1 megawatt generators powered by 1,350 hp General Motors V16-278A diesel engines. The EMD 567 used in the FT was a very similar V16 engine with 8.5" diameter cylinders but a 10" stroke and 45° vee in comparison to the 10.5" stroke and 40° vee of the submarine engines. The four diesel-electric generators powering a World War II fleet submarine corresponded to the popular A-B-B-A configuration of FTs being manufactured at the same time.
FTs were generally marketed as semi-permanently coupled A-B sets (a lead unit and a cabless booster connected by a solid drawbar) making a single locomotive of 2,700 hp. Many railroads used pairs of these sets back to back to make up a four-unit A-B-B-A locomotive rated at 5,400 hp . Some railroads purchased semi-permanently coupled A-B-A three-unit sets of 4,050 hp, while a few, like the Santa Fe, ordered all their FTs with regular couplers on both ends of each unit for added flexibility. All units in a consist could be run from one cab; multiple unit (MU) control systems linked the units together. "Hostler" controls were an option for B units, enabling these units to be operated independently of A units for moving within yard limits.