Built in 1941 by the American Locomotive Company at a cost of $265,000.00, number 4006 is one of 25 "big boys," the largest successful steam locomotives ever built, with a total weight over 600 tons. It is 132'9 1/4" long, carries 33 tons of coal and 25,000 gallons of water in its tender, and is a 4-8-8-4 (simple) articulated locomotive.