Alco 4-8-8-4 no. X4017 Big Boy
Photographed on 1 August 2003 at the National Railroad Museum, Green Bay, Wisconsin.
Built in 1941 by the American Locomotive Company for the Union Pacific Railroad, this is one of a batch of the heaviest steam locomotives ever built,weighing 772,000 lbs (386 tons). These engines were designed to be used in the Wasatch Mountains in the west, to avoid using helper (banking) engines.
The Big Boy is one of the best represented and preserved model of steam locomotive in the United States, due to its mythical reputation and late survival in service to 1959. Eight of the 25 built still exist.
Picture added on 23 November 2008