ALCO RSD-4

The ALCO RSD-4 was a 1,600 horsepower six-axle diesel-electric locomotive built by the American Locomotive Company between 1951 and 1952. It was a derivative of the four-axle RS-3 with two additional powered axles, which allowed better tractive effort at lower speeds. Because its main generator had inadequate capacity, the model was soon superseded in production by the RSD-5. The only RSD-4 that has survived is Kennecott Copper Corporation 201, which stood at the Northwest Railway Museum in Snoqualmie, Washington, until November 2021 and has since been returned to Ely, Nevada, to the Nevada Northern Railway Museum.