Union Pacific Steam

Union Pacific's steam program traces to 1960, when railroad leaders recognized the value of keeping steam alive for special activities and retained No. 844 — the last steam locomotive delivered to the railroad, in December 1944 — as the kernel of what became the UP heritage fleet; 844 remains the only steam locomotive never retired by a North American Class I railroad. The program grew in March 1981 when a group of Union Pacific employees returned Challenger No. 3985 to operating condition after years on display beside the Cheyenne depot, then the largest operating steam power anywhere; 3985 was retired from excursion service in January 2020 and donated in 2022 to the Railroading Heritage of Midwest America. The program's modern landmark came when UP re-acquired Big Boy No. 4014 in 2013 from its longtime display home in Pomona, California, and restored it at the Steam Shop in Cheyenne, Wyoming. In May 2019 — after nearly six decades dormant — 4014 moved under its own power and launched its first excursion, "The Great Race to Ogden," reclaiming for the program the title of world's largest operational steam locomotive.