The Big Boys were built for power. Theses 1.2 million pound, 6,200 horsepower locomotives did the work of three smaller engines, pulling 120-car, 3800 ton freight trains at forty miles per hour in the mountains of Utah and Wyoming.
Union Pacific
No. 4012 Big Boy
Big Boy was the name of the Union Pacific Railroad's 4000-class 4-8-8-4 articulated steam locomotives, built between 1941 and 1944 by American Locomotive Company (Alco). The 25 Union Pacific Big Boys were the only locomotives to use the 4-8-8-4 wheel arrangement.