Union Pacific Challenger

The Union Pacific Challengers were simple articulated 4-6-6-4 steam locomotives that the American Locomotive Company built from 1936 to 1944 for the Union Pacific Railroad. The railroad wanted powerful engines that could climb mountain grades at high speed, and the Challengers worked at boiler pressures and with 69 inch drivers more usual on passenger engines, often running above 60 miles per hour. Union Pacific ordered 105 in five batches, two of light and three of heavy design, and their experience led to the Big Boy of 1941 and a redesign of the last three orders. Only two survive, number 3977 on display in North Platte and number 3985, now being restored again.