The EMD SW1 is a 600-horsepower (450 kW) diesel-electric switcher locomotive built by General Motors' Electro-Motive Division between December 1938 and November 1953. It was the first to feature a General Motors prime mover, the 567 and 567A, and began EMD's modern line of switchers that continued through the later MP15 series.
The SW1 was quite popular with a total of 661 models produced and sold over the years before production on them ceased.
Today, SW1s can still be found in all types of applications, from regular freight service to industrial settings. Some have even been preserved and can found at various museums and heritage railways pulling excursions and tourist trains.