Twenty-five huge "Big Boys" were built for the Union Pacific Railroad and operated between Ogden, Utah and Cheyenne, Wyo.
Big Boy No. 4014 was delivered to the Union Pacific in December 1941 and was retired exactly 20 years later, having traveled 1,659,564 km in its 20 years of service.Union Pacific repurchased No. 4014 from the RailGiants Museum in Pomona, California in 2013 and relocated it to Cheyenne to begin a multi-year restoration process. It returned to service in May 2019 to celebrate the 150th anniversary of the completion of the transcontinental railroad.