Postwar increases in the price of both coal and labor and the efficiency of diesel-electric motive power foretold a limited life for the Big Boys, but they were among the last steam locomotives taken out of service.
Union Pacific
No. 4012 Big Boy
ALCO delivered the first batch of 20, including No. 4012, in 1941 and the remaining 5 in 1944. Eight of the 25 Union Pacific Big Boys still exist.