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The EMD SW1 is a 600-horsepower (450 kW) diesel-electric switcher locomotive built by General Motors' Electro-Motive Corporation (later Division) between December 1938 and November 1953. Final assembly was at EMD's plant at LaGrange (McCook) Illinois. The SW1 was the second generation of 3,402 cu in (55.75 L) switcher from EMD, succeeding the SC (cast frame) and SW (welded frame). The most significant change from those earlier models was the use of an engine of EMD's own design, the then-new 567 engine, here in 600 hp (450 kW) V6 form. 661 locomotives of this design were built, not withstanding diesel switcher production having been suspended between 1942 and 1945 by the War Production Board, as the 567 engines were needed elsewhere, mainly for U.S. Navy LST vessels.
Engine and powertrain
The SW1 introduced a 6-cylinder version of the 567 (later 567A) series engine to EMC/EMD switchers. Developing 600-horsepower (450 kW) at 800 rpm., this engine remained in production until 1966. Designed specifically for railroad locomotives, this was a supercharged 2 stroke 45 degree V type, with an 8 1⁄2 by 10 in (216 by 254 mm), bore by stroke, giving 567 cubic inches (9.29 L) displacement per cylinder. A D.C. generator provides power to four motors, two on each truck, in a B-B arrangement. The SW1, like most EMD switchers, use the AAR Type A switcher truck. EMC/EMD has built all its own components since 1939.
Like most long-running locomotive models, a number of changes were made to the SW1 over its production life. Internally, the post-1945 locomotives were somewhat improved, and used an updated 567A engine.
One easily spotted change is the shape of the two center cab windows over the hood, which were curved to follow the roofline originally, but became flat-topped after mid-1950. Another easily seen is the taper of the hood to the cab, which was a two-stage taper in earlier units but became a single taper in later production. Very early locomotives were delivered with a stubby exhaust stack, but this did not lift the diesel exhaust sufficiently clear of crew visibility. All later units were delivered with EMD's standard conical switcher stack, while early units were generally modified with taller stacks too. Early locomotives had a single large headlight, while later had twin sealed-beam headlights.
The SW1 appears very similar to its SC and SW predecessors, but has only a single stack instead of two, a significantly shorter hood and a larger rear platform, no small louvers on the front top hood sides, and a large grille instead of lifting vents on top of the hood front. The sandbox in front of the radiator is somewhat smaller on the SW1.
Compared to later EMD switchers, the SW1 has a much shorter hood, large platforms at each end, a single exhaust stack, and a large 'satchel' type sandbox.
- There were 7 units built as EMD demonstrators: #152 (to Scullin Steel #6), 700 (to Manufacturers' Junction Railway #7), 755 (to Inland Steel #51), 804 (to Southern Pacific Railroad #1000, pictured above), 905 (to Central of Georgia #1), 906 (to Western Pacific Railroad #501), 911 (to Great Lakes Steel #11)
- As of 2013, Amtrak still has one SW1 on their roster. #737 is used for switching chores at the Wilmington Delaware shops.
- The first SW1 built by EMC in 1939 is now preserved at the California State Railroad Museum in Sacramento, California. The locomotive worked for Holly Sugar in Santa Ana and Tracy as the company's number 1. The museum donation was a coordinated effort between the museum, the Pacific Coast Chapter of the Railway and Locomotive Historical Society and Spreckels Sugar (the locomotive's last owner).
- EMC demonstrator 906, sold to the Western Pacific Railroad as their 501, is preserved at the Western Pacific Railroad Museum at Portola, CA. It has been restored back to its original WP image. This locomotive was the Western Pacific's first diesel-electric engine.
- Another former Western Pacific SW1 is also preserved at the California State Railroad Museum. Later sold to WP subsidiary Sacramento Northern, this engine is preserved as SN 402, painted in the famous silver and orange "Zephyr" colors that the WP roads used through the 1950s and 1960s.
- The Zanesville & Western Scenic Railroad Operates a preserved SW1 on its scenic line in Fultonham, Ohio.
- The Wilmington and Western Railroad owns and operates two SW1s in tourist passenger service. One is from the Baltimore and Ohio, and the other is from the Lehigh Valley.
- The Baltimore & Ohio Railroad Museum, Baltimore, MD has former SW1 Pere Marquette Railway #11 in operating condition at last report.
- The Milwaukee Road Heritage Center operates a Black (Soon to be Painted into MILW Road's paint scheme) SW1 that was former NSP Northern States Power X-5, Ex-Burlington Northern 79, Exx- Chicago Burlington & Quincy 9137. Built in June 1939, the locomotive is in running condition, with its original Electro-Motive Division 6-567B-1 Prime Mover.
- The Indiana Transportation Museum owns two SW1's, Monon Railroad #50 the first diesel locomotive to run on the Monon, Operating, & ITMZ #860 currently waiting for restoration (ex-Cenex Harvest States Cooperative #860, exx-Milwaukee Road #867).
- The Illinois Railway Museum has former Commonwealth Edison SW1 #15. This unit is in operating condition and is one of the most frequently used diesels on the property.
- The Minnesota Transportation Museum operates Andersen Windowalls 3110, which was donated by the Andersen Corporation in 2001. It was previously Norfolk and Western Railway 3110 and originally Wabash Railroad 110, built in June 1949.
- Metra commuter rail inherited two SW1s from the Rock Island. The two engines are used for Yard Service and power on work trains on the Metra Electric and Rock Island lines. Built in 1939 and 1945, they are rumored to be two of the oldest operating diesels in Illinois.
- FirstLight Power Resources actively operates a yellow SW1 with road number 1849 as a coal train yard switcher at the Mt. Tom Power Plant in Holyoke, Massachusetts This is ex Boston & Maine #1113.[needs update]
- Sahara Coal SW1 #6 was purchased in the 1990s by the Crab Orchard and Egyptian Railroad in Marion, Illinois and is still in operation.
- Southern Pacific #1006 is at the Orange Empire Railway Museum.
- Peabody Coal Company #470 (Former Delaware, Lackawanna and Western #436) is on static display at the Museum of the Coal Industry in Lynnville, Indiana. 
- The New Hope & Ivyland Railway in New Hope, PA owns ex-Pennsylvania Railroad No. 9423.
- Pinkepank, Jerry A (1973). The Second Diesel Spotter’s Guide. Kalmbach Books. pp. 10, 26, 35. LCCN 66-22894.
- Ross, David, ed. (2003). The Encyclopedia of Trains and Locomotives. p. 264. ISBN 978-0-7607-9679-5.
- Pinkepank, Jerry A (1973). The Second Diesel Spotter’s Guide. Kalmbach Books. p. 35. LCCN 66-22894.
- "Museum Projects". www.lynnvillecoalmuseum.org. Retrieved 2017-02-25.
- Dorin, Patrick C. (1972). Chicago and North Western Power. Burbank, California: Superior Publishing. p. 96. ISBN 0-87564-715-4.
- Pinkepank, Jerry A. (1973). The Second Diesel Spotter’s Guide. Milwaukee, WI: Kalmbach Publishing Company. ISBN 0-89024-026-4.
- (July 2005), "Preservation Briefs", Trains Magazine, p. 71.
- TrainWeb.com. The Unofficial EMD homepage. Retrieved on January 7, 2005. Contains fairly complete builders' records for early EMD production.
- Andersen Windows 3110. Retrieved on December 7, 2012
- Media related to EMD SW1 locomotives at Wikimedia Commons