​ The Alco RSD-15 is a diesel-electric locomotive built by the American Locomotive Company (ALCO) of Schenectady, New York between August 1956 and June 1960, during which time 75 locomotives were produced. The RSD-15 was powered by an Alco 251 16-cylinder four-cycle V-type prime mover rated at 2,400 horsepower. The locomotive rode on a pair of three-axle Trimount trucks with all axles powered by General Electric model 752 traction motors. These particular trucks have an asymmetrical axle spacing due to the positioning of the three traction motors. The six-motor design allowed higher tractive effort at lower speeds than an otherwise similar four-motor design. The RSD-15 could be ordered with either a high or low short hood; railfans dubbed the low short hood version "Alligators" due to their unusually long low noses. Santa Fe ordered 50 of these locomotives (800-849) all with the low nose configuration. These versatile locomotives were known as a jack-of-all-trades as they were suited for mainline freight, passenger service, and even yard switching duties.

Broadway Limited Santa Fe RSD-15 Alligators