Union Pacific's Big Boy 4-8-8-4 4014 returned to the mainline in August and September 2021 with a mainline tour to New Orleans and St. Louis. On the final leg of its 2021 mainline tour, the world's largest operable steam engine was on the home stretch back to its homebase in Cheyenne, WY. Heading north from Denver, CO, the Big Boy once again put on an impressive show as it returned home.
