Topic summary
Union Pacific Big Boy
The Union Pacific Big Boy is a type of simple articulated4-8-8-4steam locomotive manufactured by the American Locomotive Company (ALCO) in Schenectady, New York, between 1941 and 1944 and operated by the Union Pacific Railroad in revenue service until July 1959.
The 25 Big Boy locomotives were built to haul freight over the Wasatch Range between Ogden, Utah, and Green River, Wyoming. In the late 1940s, they were reassigned to Cheyenne, Wyoming, where they hauled freight over Sherman Hill to Laramie, Wyoming. They were the only locomotives to use a 4-8-8-4 wheel arrangement: four-wheel leading truck for stability entering curves, two sets of eight driving wheels and a four-wheel trailing truck to support the large firebox.
Eight Big Boys survive, with most on static display at museums across the United States. One of them, No. 4014, was re-acquired by Union Pacific, and by 2019 was rebuilt to operating condition for the 150th anniversary of the first transcontinental railroad. It thus regained the title as the largest and most powerful operational steam locomotive in the world.