Built by General Motors Electro-Motive Division (EMD), the SW1500 is powered by the 645-series diesel prime mover. This series of prime movers have proven to be extremely reliable and have withstood the rigors of time. Today, after 45 years of use most of the engines are still in service.

Originally intended for short distance switching duties, the bulky EMD SW1500 was close to road switcher abilities and in many cases operated in this role for branch line services.

Production of the SW1500 peaked in 1972 with 189 units produced but the model became a casualty of 1970s skyrocketing inflation shortly after. With costs spiraling, a unit dedicated primarily to switching was not proving to be cost effective. Instead the design was revamped and evolved into the MP15 which could be used both for yard and road service.