Union Pacific Is Rebuilding Its Largest Steam Locomotive

'Big Boy' 4014 is being restored to celebrate the 150th anniversary of the Transcontinental Railroad.

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The Union Pacific Railroad is restoring one of its last remaining steam engines, one of the largest in the world, to celebrate the 150th anniversary of the completion of the Transcontinental Railroad, reports Atlas Obscura.

Unlike the steam engines that met head-on in Promontory, Utah in 1869 when the Transcontinental Railroad was completed, the Big Boys were built in the 1940s and were among the last steam engines in use. They were built to address the need for more power to pull long trains over the mountains. Multiple locomotives were usually used, but each locomotive required its own crew and more fuel. The Big Boy was designed to have enough power to handle these mountain passes all by itself.

The Big Boys operated from 1941 through 1959 when they were replaced with diesel-electric locomotives. Most of the huge steam engines were scrapped, but eight were spared and put on display in museums around the country. 

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Union Pacific steam crew members lay temporary track panels for Union Pacific's Big Boy No. 4014 (background) at the Fairplex on November 14, 2013 in Pomona, California.

In 2013, Union Pacific announced that it would be restoring Big Boy 4014 with the intention of having it ready by May 10, 2019, the 150th anniversary of the completion of the Transcontinental Railroad.

Union Pacific 4014 is an appropriately named "Big Boy" locomotive. It is 132 feet, 9 inches long, and weighs over one million pounds. It has two sets of eight drive wheels, plus two sets of four wheels in front and behind them. When U.P. 4014 makes its trip to Utah next year it will be the first time it has run in 60 years.

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