Union Pacific 4012, Steam locomotive at Steamtown National Historic Site, United States
Union Pacific 4012 is a Big Boy steam locomotive on static display at Steamtown National Historic Site in Scranton, Pennsylvania. It runs on a 4-8-8-4 wheel arrangement, meaning it has two sets of eight driving wheels, giving it the power to pull heavy freight over mountain grades.
The locomotive was built in 1941 by the American Locomotive Company to handle freight on the steep grades between Wyoming and Utah. It was taken out of service in 1962 when diesel engines fully replaced steam across the rail network.
The Union Pacific 4012 belongs to the class known as 'Big Boy', a nickname given by workers at the factory where these locomotives were built. The name stuck and became widely used, so much so that even Union Pacific eventually adopted it officially.
The locomotive sits outdoors on the Steamtown grounds and can be viewed up close from multiple angles. A clear day makes it easier to take in the full scale of the machine and notice the details on the wheels and bodywork.
Only 25 Big Boy locomotives were ever built, and Union Pacific 4012 is one of the few that survived intact. Its body is split at a pivot point in the middle, allowing it to bend slightly on curves, which is an unusual feature for a machine of this size.
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