The Milwaukee Road S3 Class was a class of 10 4-8-4 "Northern" type steam locomotives built by the American Locomotive Company in 1944 and operated by the Milwaukee Road until the mid 1950s. The locomotives saw service in pulling freight and passenger trains throughout the Milwaukee Road. Today, two S3s survive, No. 261 is in operating condition and No. 265 is on display in Union, Illinois. History The Milwaukee Road had acquired its first four-unit EMD FT diesel set in October 1941. It had managed to get a second in July 1943, but when it wanted more in 1944, it was only allocated six by the War Production Board. Instead, it was allocated ten Alco 4-8-4 locomotives. These were delivered in July and September 1944, and were classified as class S3 by the Milwaukee Road. Design Alco had drafted a compromise design, as the WPB has placed a moratorium on creating completely new designs. It was based on the frame of the Chicago, Rock Island and Pacific Railroad class R67B, mated to the boiler of the Delaware and Hudson Railway class K. The tender was a water-bottom type with a pair of six-wheel trucks. They were also fitted with an air horn. The of coal-burning grate supplied heat the boiler which was pressed to . This supplied steam to the cylinders which had a bore of and a stroke of . They were connected to the diameter driving wheels by Walschaerts valve gear. While they were smaller and less powerful than the Milwaukee's earlier class S2, they were comparable to road's first class of 4-8-4, the class S1 and were equipped with roller bearings. Construction All ten were built by Alco's Schenectady plant in July (7) and September 1944 (3). Alco assigned order number S-1928 and serial numbers 71973 through 71982. Service Initially they were used as freight locomotives, and only used on lines east of the electrified zone, being allocated to the Dubuque and Illinois Division. As a consequence of the Korean War, additional locomotives were needed on the Idaho Division, so four locomotives (262, 263, 267 and 269) were converted to oil firing and sent west to work passenger and freight trains in the gap between the two electrified zones. By March 1954, No. 260 had been transferred to the La Crosse and River Division, and 261 was on the Milwaukee Division; the other four coal-burners were still