c. 1931, weighing , engine only. At , the Illinois Central Railroad's 2800 class rebuilds probably had the highest calculated tractive effort of any two-cylinder steam locomotive, although the adhesive weight was only . The Baltimore and Ohio Railroad ordered its first from Baldwin in 1914. From 1914 to 1956, their bore numbers commencing with 6, hence the nickname "Big Sixes". Designated the S class, there were several sub-classes. The first of the Big Sixes was retired in 1951 and were all scrapped by 1960. The Southern Railway (SOU) ordered its first batches of fifty-five 2-10-2 Ss class steam locomotives (Nos. 5000-5054) from Baldwin in 1917. The second batches of twenty-five 2-10-2s (Nos. 6350-6374) were built by the American Locomotive Company's (ALCO) Richmond Works in 1918 originally for SOU's Cincinnati, New Orleans and Texas Pacific (CNO&TP) division. The latter batches were later moved to the SOU's main division and renumbered to 5055-5079 when they were proved to be too bulky for the CNO&TP tunnels' tight clearances. After receiving the last batches of Ss types, the SOU received fifty more 2-10-2s (Nos. 5200-5249) from ALCO's Brook Works in a USRA Light Santa Fe design which were classified as Ss-1. Both classes were assigned to SOU's Asheville division, banking and hauling heavy freight trains up the steep Saluda Grade and Old Fort Loops in the Blue Ridge Mountains. Between the late 1930s and the early 1950s, all of the Ss and Ss-1 steam locomotives were retired and scrapped with none surviving into preservation. The Union Pacific Railroad rostered 144 2-10-2 locomotives, under the designation of TTT (Two-Ten-Two). They were divided into classes TTT-1 through TTT-7, but all had the same cylinder dimensions, driving wheel diameter and boiler pressure. Of these, only one locomotive survives; Union Pacific 5511 was donated to the Railroading Heritage of Midwest America, who plans to restore the locomotive to operating condition. References 10,2-10-2