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September 4, 1941

UP Receives 1st Big Boy Steam Locomotive

By 1940, the National Defense Act encouraged railroads to develop faster, more powerful locomotives in preparation for wartime requirements. Union Pacific responded with the 4-8-8-4 Class 4000 Big Boy, a 132-foot long, 1.2 million-pound hulk. Because of its great length, the frame was articulated, or hinged, to allow it to negotiate curves. Its power was ideally suited to climb the 1.14 percent grade of the Wasatch Mountains. The last Big Boy made its final run in July 1959.

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Although no Big Boys are operating today, eight have been donated for public display in various cities around the country. They can be found in Pomona, Calif.; St. Louis, Mo.; Dallas, Texas; Omaha, Neb.; Denver, Colo.; Scranton, Pa.; Green Bay, Wis.; and Cheyenne, Wyo.

In 2012, Union Pacific celebrates the shared stories that have shaped our country since 1862. To mark our 150th anniversary, we invite you to explore how the nation’s largest railroad came to be and how UP continues to build America with innovation and tenacity, touching the lives of nearly every citizen.