History of the 4-8-8-4 Big Boy

    The Union Pacific railroad operated freight service between Ogden, Utah, and Evanston, Wyo. This 75 mile stretch of track climbed through the Wasatch Mountains on grades of 1 percent or better. The heavy loads often  required double heading to make the grade at the posted speed limits of 35 to 45 miles per hour. UP was constantly searching for an engine that could keep up with ever increasing train sizes. So in 1940 they contracted with ALCO to design what would end up being the largest locomotive ever built. The famous 4-8-8-4 Big Boy.

    The Big Boy is 132 feet long and weighs 1.2 million pounds. It is called a 4-8-8-4 because of the configuration of it's wheels. The first set of four wheels on the forward section were the pilot wheels that guided the engine. Then there were two sets of eight driving wheels and finally another set of four wheels supporting the rear of the locomotive. Hence the designation 4-8-8-4.

    The name Big Boy was adopted for the engine because someone at the factory had written "Big Boy" on the smoke box door of one of the first engines produced. The name stuck and from then on the giant engines were known as the Big Boys.

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