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The earliest 4-6-2s were built by the Baldwin Locomotive Works in 1901 for 3-foot ... and 4-8-4s. The Reading Co. became the last U.S. railroad to receive a fleet of Pacifics in 1948.

There are steam locomotives, and then there’s “Big Boy.” At 604 tons and 132 feet long and with a 4-8-8-4-wheel arrangement, it is the largest, most powerful steam locomotive in the world.