Twenty-five Big Boys were built exclusively for Union Pacific Railroad, the first of which was delivered in 1941. The locomotives were 132 feet long and weighed 1.2 million pounds. Big Boy No. 4014 was delivered to Union Pacific in December 1941. The locomotive was retired in December 1961, having traveled 1,031,205 miles in its 20 years in service. Union Pacific reacquired No. 4014 from the RailGiants Museum in Pomona, California, in 2013, and relocated it back to Cheyenne to begin a multi-year restoration process. It returned to service in May 2019 to celebrate the 150th Anniversary of the Transcontinental Railroad's Completion. This is the first time Big Boy has gone on tour since its post-restoration debut in 2019 to celebrate the 150th anniversary of the transcontinental railroad's completion.
