When the U.S. entered World War II The American railroads saw increases in traffic. The
Baltimore and Ohio Railroad, along with other railroads, wanted to purchase more
diesel, as the technology was rapidly improving to the point that it would soon surpass steam locomotives. But the War Production Board regulated the production of steam and diesel locomotives until the war emergency was over. So, alongside the production of 40 new class T-3 4-8-2 type locomotives built at the railroad's own Mt. Clare shops, the B&O ordered 30
class EM-1 Yellowstones from Baldwin in 1944 and 1945, becoming the smallest, most numerous, and most modern of this type. The EM-1 produced of tractive effort on drivers with steam pressure and four cylinders. The tender carried of water and 25 tons of coal. The engine weighed while the tender weighed for a combined . Nothing bigger could operate within the tunnel clearances and track restrictions on the B&O's main line. They were equipped with the newest technology of the time. They featured the Worthington feedwater heater, superheater with front-end throttle, Cyclone front end, thermic syphons, a lateral cushioning device in the front pair of drivers on both engines and the front wheels and the trailing truck, and roller bearings on all axles, engine and tender. The latter gave them the reputation of "yard creepers", because three men could move one on a level track with the cylinder cocks open. B&O's president, Roy B. White, after inspecting the first one delivered, said to the general superintendent of motive power and equipment, A.K. Galloway, "Well, I must say, they have everything!" Fleet numbers 7600–7619 were built and delivered in 1944 and 7620–7629 in 1945, all by the Baldwin Locomotive Works of Philadelphia, Pennsylvania. They went to work on the Cumberland Division's rugged West End subdivision with its more than 2% grades and tight curves, where they supplemented older 2-8-8-0 EL classes on West Virginia coal and freights. Since the EM-1s had roller bearings throughout, they handled mail and express trains too, replacing two T-3s in this role. In January 21, 1947, when, near Oakland, Maryland, train 29 with engine 7625 derailed with the locomotive rolling onto the engineer's side, killing the engineer. After this accident, the EM-1s were restricted to coal and freight trains in regular service for the rest of their working lives. However, the B&O would use EM-1 No. 7600 for railfan trips in the late 1950s. The EM-1s also ran on the Pittsburgh Division over Sand Patch Grade near Meyersdale, Pennsylvania. While they mainly hauled general freight workings here, they were best known for pulling loads of iron ore or dolomite westbound, or coal eastbound. In the late 1950s, the B&O used EM-1 No. 7600 for railfan trips mostly between Cumberland, MD, and Connellsville, PA. Well-known photographer and Cumberland, MD native William P. Price captured, on still pictures and 8mm films, the EM-1s on the east side of Sand Patch pulling heavy trains with two of the B&O's 2-10-2 class S1 and S1a Big Sixes on the rear as helpers dispatched from Hyndman, PA. Near the end of steam they were all sent out to Fairmont and Wheeling, West Virginia, and Lorain, Ohio, with lake-bound coal trains as well as runs between Willard, OH and Garrett, Indiana, until the B&O retired them from 1957. Two engines, 650 (7600) and 659 (7609), were subjects of preservation attempts, but neither succeeded. No. 650 (7600) was earmarked for preservation by the
B&O Railroad Museum in
Baltimore, but a yard master mistakenly interpreted the order for the engine's move to the museum as one for the engine to be taken to the scrapyard. No. 650 was broken up, and the yard master was fired soon after. No. 659 (7609) was offered to the city of
Wheeling,
West Virginia for static display. The city turned down the offer, and the engine was scrapped. Thus, none of the EM-1s survive today. ==Outside the United States==