The EMD SW1 is a 600-horsepower (450 kW) diesel-electricswitcher locomotive built by General Motors' Electro-Motive Corporation (later Division) between December 1938 and November 1953. Final assembly was at EMD's plant at LaGrange (McCook) Illinois. The SW1 was the second generation of 3,402 cu in (55.75 L) switcher from EMD, succeeding the SC (cast frame) and SW (welded frame). The most significant change from those earlier models was the use of an engine of EMD's own design, the then-new 567 engine, here in 600 hp (450 kW) V6 form. 661 locomotives of this design were built,[1] with a gap in production between March 1943 and September 1945 due to World War II.
The SW1 was the start of a long line of SW series switchers produced by EMD. It was complemented by the SW7 in 1949 and the SW8 in 1950.[1] SW1 production ceased in November 1953, with its replacement, the equally powerful SW600, starting production in February 1954.[1]