Built in 1941 Big Boy was designed especially for use by the Union Pacific Railroad on its rugged Cheyenne to Ogden, Utah run. The mighty 4004 was one of a series of only 25 locomotives of this type ever built. It was retired from service on December 21, 1956.

Total weight 1,208,750 lbs. Overall length-132’ 93/8”. Fuel capacity—28 Tons. Water capacity—25,000 Gals.