The EMD SW9 is a classic North American diesel-electric switcher locomotive that became one of Electro-Motive Division’s (EMD) most successful yard power designs of the early post-war era. Built between November 1950 and December 1953 by General Motors Electro-Motive Division in the United States, with additional units constructed by General Motors Diesel (GMD) in Ontario, Canada, the SW9 was designed primarily for yard switching, industrial service, and light transfer work.
Powered by an EMD 12-567B 12-cylinder two-stroke diesel engine producing 1,200 hp, the SW9 delivered dependable performance with robust low-speed tractive effort suited to frequent starts and stops typical of switching duty. Unlike its predecessor, the SW7, the SW9 lacked the upper hood vents and generally featured improved internal components, and late in production some units received a 567BC variant of the prime mover (with one final unit even equipped with a full 567C).
During its relatively short production run, about 786 units were built for American railroads and 29 for Canadian operators, making it one of the more widely seen medium-power switchers of the era. The locomotive rode on B-B (four-axle) trucks and was adaptable enough that some railroads acquired paired “cow-calf” sets (TR5) where two units were semipermanently coupled for heavier switching tasks.
Railroads appreciated the SW9 for its versatility, reliability, and ease of maintenance, traits that kept many in service for decades; numerous examples continued to work on short lines, industrial properties, and even on excursion or heritage assignments long after their Class I careers ended.
Key characteristics of the EMD SW9 include:
- Power output: ~1,200 hp from an EMD 12-567B prime mover (some later units had 567BC/C)
- Builder: EMD (USA) and GMD (Canada)
- Production years: November 1950 – December 1953
- Total built: ~815 units (U.S. + Canada)
- Wheel arrangement: B-B (four axles)
Overall, the SW9 represents an important step in post-war dieselization, bridging earlier medium-power switchers and later models like the SW1200, which adopted more refined engines and extended production well into the 1960s.
