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.