Here's the Biggest Steam Engine in the World Going on a Test Run For the First Time in Nearly 60 Years

Union Pacific 4014, also known as the one of the only 25 Big Boys ever built and only eight still in existence, is now officially the only one running in the world. Earlier we heard it blow its whistle for the first time since 1962, and yesterday evening it went for its first test run under its own power for the first time in 57 years. And weighing in at over a million pounds, it is now officially the largest running steam engine in the world.

Each Big Boy wasn’t just designed to be large, weighing as much as 1,200,000 pounds, as an aesthetic thing. They were so big because they were enormously powerful, as Railway Age noted in a story about UP4014 when it was first announced that it would be restored:

Twenty-five Big Boys were built exclusively for Union Pacific by the American Locomotive Company (Alco) between 1941 and 1944, in two groups of ten and one of five. All burned coal, with large, 150-square-foot grates to burn the low-quality Wyoming coal from mines owned by the railroad. They were designed to pull long, heavy freight trains (maximum rated tonnage of 4,040 tons) at a sustained speed of 60 mph once past the Wasatch Range mountain grades on UP’s main line between Ogden, Utah, and Cheyenne. Peak horsepower was reached at about 35 mph; optimal tractive effort at about 10 mph.


Using nothing but the power of fire and boiling water, it produced 6,300 horsepower when new.

Image: Union Pacific

But, like I said, that was many moons ago. Union Pacific 4014 has been sitting for a long, long time. Until yesterday, when it was fired up and ran down the main line once again.

UP4014 ran coal for Union Pacific for 20 years, from December 1941 to December 1961, at which point the company donated it to the Railway and Locomotive Historical Society and the RailGiants museum in Southern California. Which is where it sat, and sat, and sat, for decades. Even though it was working when it got there, and it was relatively well maintained by the museum, the decades are never kind to massive complex machinery that’s exposed to the elements. So it needed some work at Union Pacific’s facility in Cheyenne, Wyoming.

Astute observers of geography will note, however, that “Wyoming” is not a place in California, let alone one immediately adjacent to the RailGiants Museum in Pomona, California. To get it from Pomona to the shop in Cheyenne was an ordeal in and of itself.

Actually, let me correct that. Just moving it across the parking lot was an ordeal. No, seriously, Union Pacific had to move it across a parking lot before the Big Boy could go anywhere at all, back in 2014 when this whole restoration process started:

At which point it had to be towed across the country by the descendants of the diesel engined locomotives that replaced it, truly an indignity for a train if there ever was one:

And then it had to be restored in a process that took more than two years:

But the good news is that it at least looks like everything is now moving smoothly, over five years later, as the Big Boy was taken on its first test run, billowing smoke and with steam pouring from seemingly every orifice:

The plan is to drive the Big Boy from Cheyenne, Wyoming, to Ogden, Utah, starting tomorrow for a five-day journey to commemorate the 150th anniversary of the transcontinental railroad in the United States.

And while this is all well and good, it’s probably best to just longingly gaze at UP 4014 through your computer screen, on Youtube. Apparently all the people trying to glimpse of it are causing serious problems, and there are ongoing fears of multiple car crashes as people try to crane their necks to get a look at it.



Deputy Editor, Jalopnik. 2002 Lexus IS300 Sportcross.



As a mechanical engineer, it boggles my mind they came up with things like this with hand drawings and slide rules. No automated machining, no 3D modelling. Just old school engineering. I couldn’t care less about modern locomotives, but there is just something about old steam locomotives.