The EMD SW900 was built directly after earlier models had completed production such as the SW9, SW8, and SW1. Also, beginning with the SW900, EMD began using the number designation of the model to refer to its horsepower rating instead of simply using it to list its sequential order in the series. The SW900's horsepower rating was not as high as its predecessor's, the SW9, which probably explains, partly anyway, why it had fewer sales. Still, nearly 400 were built for dozens of different roads and industries. As with every other model in the SW series, the SW900's reliability and versatility has allowed it to continue to find use in several industrial and short line applications even today.
To date there are officially three examples known to be preserved; Baltimore & Ohio #9408 at the Baltimore & Ohio Railroad Museum in Baltimore, Maryland (built as B&O #633 in the summer of 1955); Cuyahoga Valley Railroad/New York Central #8630 at the Midwest Railway Preservation Society (manufactured in 1956) in Cleveland, Ohio; and Coors Brewery #988 at the Colorado Railroad Museum in Golden (built as Chicago, Rock Island & Pacific #550 in January, 1957).
The EMD SW900 began production in December, 1953 and again carried the builder's traditional carbody styling with a tapered hood near the cab and just a short, 44-feet in length. Outwardly, the SW900's one striking visual difference from other models is its single, tong-shaped exhaust stack. Interestingly, this design was only featured on the SW900 and SW1200, as no other model in the SW series carried such a configuration. The SW900 came equipped with EMD's model 567C prime mover which, as mentioned earlier, could produce 900 horsepower (a slight downgrade from the SW9's 1,200 horsepower). The model featured a new traction motor, General Motors' model D37B, which could produce 36,000 pounds of continuous tractive effort and 57,500 pounds starting (also a downgrade from the SW9's 62,000 pounds).
Sales for the EMD SW900 were respectable but not nearly as high as the earlier SW9. It seems that EMD's 1,000-1,200 horsepower models were the perfect fit for railroads, as they nearly always saw the highest numbers (likely due to the fact that the extra horsepower not only allowed the locomotives to shuffle more cars but also be used in occasional freight operations). In any event, the SW900 would still find a variety of buyers with several Class Is, shortlines, and industries purchasing it. By the time the SW900 hit the market in late 1953 EMD's reputation for building high quality switchers, and diesel locomotives in general, was well-known. Once again EMD did not disappoint with the model as it remained a reliable and versatile locomotive that was easy to maintain and could operate about anywhere with a weight of just 115-tons.
Interestingly, EMD had intended to also build another cow/calf model with the SW900, as it had with most other earlier designs (up to that point it offered a version ranging from TR through TR6). However, either the builder could not gain any interest in the locomotive or did not believe many sales would transpire (few of the TR models actually sold many sets) and ultimately decided not to offer the TR9 model. Of note, the company's Ontario division, General Motors Diesel, was also able to sell a batch of SW900s, nearly 100. The GMD models were purchased by Algoma Steel, Aluminum Company of Canada, British Columbia Electric Railway, Canadian Pacific, Canadian National, McKinnon Industries, Midland Railway Company of Manitoba, and Steel Company of Canada.
The EMD SW900 had a very long production run and when the final model rolled out of LaGrange, Illinois bound for shortline Lancaster & Chester in early 1969, some 371 had been built (including 97 built at General Motors Diesel. Today, you can still find SW900s (aside from those preserved) in operation on the Wilmington & Western, Armco Steel, Southern Railway of British Columbia, Lancaster & Chester, Cargill, Aberdeen, Carolina & Western, Ellis & Eastern, Juniata Valley, Adrian & Blissfield, Huntsville - Madison County Airport Authority, CMI Steel, Milford-Bennington Railroad, Richmond Pacific, Fisher Farmer's Grain & Coal, and a number of privately owners.