Big Boy was a Class 4000 steam locomotive built for the Union Pacific Railroad with 20 made in 1941, and the last 5 in 1944, all were made by the American Locomotive Company in Schenectady, New York. The working Big Boys weighed in at 1.2 million pounds, with an average of 5,900 horsepower to pull heavy loads on steep climbs. The need for such a powerful engine was specifically for the area east of Ogden, Utah, the Wasatch grade, which before had gained a reputation as “the helper district” because there wasn’t a locomotive before the Big Boy that could make the climb without using helper engines to pull them along. 

The wheel arrangement was a unique 4-8-8-4 alignment to any other locomotive, with four leading truck wheels for stabilization followed by two sets of eight driving wheels and ending with four supporting trailing truck wheels allowing turns up to 20 degrees. The Big Boy was known to regularly haul loads up to 4,040 tons through the late 1950’s with all engines logging more than one million miles each by the time of their forced retirement due to creation of diesel-electric engines.  The iconic Big Boy would remain one of the most successful steam locomotives ever produced.