1. Home
 ›
2. Diesel Locomotives
 ›
3. SW1200

EMD "SW1200" Locomotives: Data, Specs, Roster

Last revised: January 10, 2025

By: Adam Burns

The SW1200 was pinnacle of Electro-Motive's switcher line featuring its 567 power plant.  It was the final model to feature the engine and also the most successful with a total of 1,039 units produced between 1954 and 1966.

EMD's system for designating its switchers was not consistent, particularly in the early years, which makes deciphering each models' lettering and numbering somewhat difficult.

However, the SW1200 was a straightforward moniker with "SW" denoting "switcher" and 1,200 the horsepower rating.  Once more, EMD enjoyed strong sales with this model as a variety of railroads and private industries purchased the locomotive. 

Today, just as with virtually every other model in the series, SW1200's can continue to be found hauling freight for short lines and used in industrial settings, along with also pulling excursion trains. 

Photos

Penn Central SW1200 #9199, still in its New Haven paint (built as #659) lays over in Maybrook, New York in the fall of 1970. Note Penn Central U25B #2672 in the background, also still in its New Haven paint (built as #2512). American-Rails.com collection.

Overview

The SW1200 began production in January, 1954 around the same time as its less powerful counterpart, the SW900. The model used EMD's 567C prime mover.

The 12-cylinder engine could produce a hefty 1,200 horsepower, which proved a strong selling point.  At this rating the locomotive could be used in either switching work or even light freight duties.  This latter ability was further enhanced by optional MU capabilities.

Using General Motors' newer model D37B traction motor the SW1200 could produce a respectable 36,000 pounds of continuous tractive effort and overall weighed just over 122-tons.  

Baltimore & Ohio SW1200 #9618 wearing the Chessie System livery is seen here at Parkersburg, West Virginia on October 13, 1976. American-Rails.com collection.

Sales for the SW1200 quickly took off and with the builder's reputation at the time as the best locomotive manufacturer on the market, sales remained steady through the 1950s and even into the 1960s.

Just as with other SW series models, numerous Class Is, short lines, and private industries purchased the switcher.  In his book, "Diesel Locomotives: Cyclopedia, Volume 2," Bob Hayden notes the SW1200 offered a variety of options including MU (as previously mentioned), sealed-beam headlight, additional rotating headlight, Flexicoil trucks, larger fuel tank, dynamic brakes, and dual controls.

Rio Grande SW1200 #135 lays over in Salt Lake City, Utah, circa 1975. Robert Eastwood, Jr. photo. American-Rails.com collection.

After EMD released the SW9 it abandoned cataloging its cow/calf TR series although it contemplated doing so with the SW900 of 1953 but ultimately decided against doing so.

In any event, the SW1200 would also not be offered in a cow/calf variant mostly because interest in the setup had waned following the SW9.

Domestic production on the switcher continued through May, 1966 and when the last unit was outshopped some 733 units (including a Great Northern rebuild) had been produced in the United States while another 274 were built by General Motors Diesel of London, Ontario (sometimes referred to as the SW1200RS).

Milwaukee Road SW1200 #711 (built as #2037) - the only switcher to wear the company's "Milwaukee II" livery - works the Miller Job at the Muskego Yard in Milwaukee, Wisconsin during March, 1985. R.W. Brown photo. American-Rails.com collection.

There were also another 32 units built for export in South and Central America including Brazil, Panama, and Chile.

Beginning with the SW1000, EMD swapped engines for the newer model 645 prime mover.  In doing so the builder changed the carbody by featuring a hood with harder lines and less beveling, wider cab, and higher profile for improved visibility. 

Data Sheet and Specifications

Production Rosters

Electro-Motive (EMD)

(Total Built = 732)

Pennsylvania SW1200 #9011 (Class ES-12) was photographed here in Columbus, Ohio, circa 1966. Fred Byerly photo. American-Rails.com collection.

EMD Rebuild

(Total Built = 1)

SW1200's completed from trade-in units, reusing the same serials as their predecessors.

General Motors Diesel (GMD)

(Total Built = 274)

Canadian units are sometimes referred to as SW1200RS, equipped with Flexicoil trucks.

Export

 (Total Built = 32)

Sources

• Foster, Gerald. A Field Guide To Trains. New York: Houghton Mifflin, 1996.

• Hayden, Bob. Diesel Locomotives: Cyclopedia, Volume 2 (Model Railroader). Milwaukee: Kalmbach Publishing Company, 1980.

• Marre, Louis A. Diesel Locomotives: The First 50 Years, A Guide To Diesels Built Before 1972.  Milwaukee: Kalmbach Publishing Company, 1995.

• Pinkepank, Jerry A. Diesel Spotter's Guide.  Milwaukee: Kalmbach Publishing Company, 1967.

• Solomon, Brian.  EMD Locomotives.  Minneapolis: MBI Publishing Company, 2006.

Milwaukee Road SW1200 #601 carries out switching chores at what appears to be the Bensenville, Illinois terminal on May 15, 1971. Photographer unknown. American-Rails.com collection.

Unfortunately, this 8-cylinder variant's slightly longer frame and higher cab caused clearance issues for private industries.  As a result, EMD would release an updated version, the SW1001, to correct these flaws.

The SW1200's immediate successor was the 12-cylinder SW1500, a model that continued the success of its predecessor and saw more than 800 units produced at La Grange.  Today's the powerful and versatile SW1200 is still quite common in industrial settings.