Union Pacific's Big Boy No. 4014 is the largest steam locomotive running anywhere on Earth: 1.2 million pounds, 133 feet long. Only 8 of the 25 ever built survive, and only this one still runs. For 51 years it just sat as a park exhibit in Pomona, California. Union Pacific rebuilt it and put it back on the rails. This summer it crossed 14 states and 7,145 miles for America's 250th birthday. It is still running.
