The ALCO RSD-4 was a 1,600
horsepower (1.2 MW) six axle
diesel-electric locomotive built by the
American Locomotive Company between 1951 and 1952.[1] It was a derivative of the four-axle
ALCO RS-3, with two additional powered axles which allowed better tractive effort at lower speeds. Due to the inadequate capacity of the main generator, this model was later superseded in production by the
ALCO RSD-5.
The only ALCO RSD-4 that has survived is Kennecott Copper Corporation #201. It resided at the
Northwest Railway Museum until November 2021 (formerly known as the Puget Sound & Snoqualmie Valley Railway) in
Snoqualmie, Washington in its orange Kennecott paint scheme.[2] As of 2021, it has been returned to Ely, Nevada (along with
EMD SD7 #401) to the
Nevada Northern Railway Museum.[3]