Few locomotives in American history are quite as iconic as Union Pacific’s Big Boy No. 4014. As the world’s largest operating steam locomotive prepares for its first-ever coast-to-coast tour in 2026, we here at shop.trains.com are gearing up for what promises to be a once-in-a-lifetime opportunity to witness the engineering marvel in motion.
The story of the Big Boy begins in the early 1940s, when Union Pacific needed a solution for hauling heavy freight over the steep 1.14% eastbound ruling grade of Utah’s Wasatch Range. A team led by UP’s chief mechanical officer Otto Jabelmann rose to the challenge and adapted the design of the existing 4-6-6-4 Challenger locomotive to create something far more massive.
The result was the Big Boy class, which was composed of twenty-five locomotives built exclusively for Union Pacific by the American Locomotive Company (ALCO) at their Schenectady, New York works. The design enlarged the firebox to approximately 235 by 96 inches, lengthened the boiler, and added four driving wheels while reducing the diameter of those wheels from 69 to 68 inches.
No. 4014 specifically rolled out of ALCO’s facility in November 1941 at a cost of $265,174, equivalent to roughly $5.67 million in today’s dollars. Delivered to Union Pacific the following month, the locomotive entered revenue service just as America was joining World War II. These massive machines were built to haul heavy equipment in support of the war effort, normally operating between Ogden, Utah, and Cheyenne, Wyoming.
At 133 feet long and weighing 1.2 million pounds, the Big Boy is longer than two city buses and weighs more than a Boeing 747. Due to that exceptional length, the frames of the Big Boys are “hinged,” or articulated, which allows them to negotiate curves that would otherwise be impossible for such a massive machine.
The 4-8-8-4 wheel arrangement tells the story of the locomotive’s design: four wheels on the leading set of pilot wheels to guide the engine, eight drivers on the first engine, another set of eight drivers on the second engine, and four wheels trailing that support the rear of the locomotive. The Big Boy was designed for stability at 80 miles per hour, though steam locomotives of this type normally operated well below that speed in freight service.
Designed to haul 3,600-short-ton freight trains over the Wasatch Range, the Big Boys routinely exceeded expectations, pulling trains of up to 4,200 short tons. During a test on April 2, 1943, No. 4014 itself pulled 65 freight cars between Ogden, Utah, and Evanston, Wyoming, generating a maximum of 5,530 horsepower.
No. 4014’s last routine repairs took place in 1956, and the locomotive completed its final revenue run on July 21, 1959. By that time, No. 4014 had traveled an impressive 1,031,205 miles during its revenue service.
Union Pacific officially retired No. 4014 on December 7, 1961. All remaining Big Boys were retired by 1962, their duties taken over by diesel locomotives and gas turbine-electric locomotives. That same year, Union Pacific donated No. 4014 to the Southern California chapter of the Railway & Locomotive Historical Society in Pomona, California, where it became one of eight Big Boys preserved around the United States.
The seven other remaining Big Boys remain on public display in St. Louis, Missouri; Dallas, Texas; Omaha, Nebraska; Denver, Colorado; Scranton, Pennsylvania; Green Bay, Wisconsin; and Cheyenne, Wyoming.
In late 2012, Union Pacific officials announced their intention to obtain a Big Boy locomotive for restoration to operational condition for excursion service, which would wind up being No. 4014.
By early 2017, No. 4014 had been completely disassembled. New parts were fabricated, including rod brasses, top boiler check valve, and lubricator check valves. The driving wheels were sent to the Strasburg Rail Road in Pennsylvania for crankpin and axle work as well as installing new tires.
One major alteration was made during restoration: converting the coal-burning locomotive to run on No. 5 fuel oil. This was accomplished by replacing the firebox grates with a fire pan and an oil burner, making No. 4014 only the second Big Boy to undergo such a conversion.
By May of 2019, No. 4014 moved under its own power for the first time in almost 60 years, becoming the world’s largest operational steam locomotive.
The locomotive also made history in 2021 by becoming the first mainline steam locomotive to be equipped with positive train control (PTC). In May 2024, PTC equipment was installed in a cabinet in the tender, allowing No. 4014 to run without a diesel helper.
The Coast-to-Coast US 250 Tour
Union Pacific will join the nation in celebrating 250 years of American independence and innovation in 2026 with its first-ever coast-to-coast steam tour led by Big Boy No. 4014. This historic journey is the first time the Big Boy will be shared with communities on the East Coast.
The first leg of the tour starts Sunday, March 29, with the Big Boy and several historical passenger cars from Union Pacific’s Heritage Fleet traveling west to California from Cheyenne, Wyoming, the steam locomotive’s homebase. The first leg of the tour ends Friday, April 24 in Cheyenne.
Two major public display days are set for the western leg:
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Friday and Saturday, April 10-11: Roseville, California
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Saturday and Sunday, April 18-19: Ogden, Utah
A daily schedule with additional stops along with a map of the route will be released closer to the tour’s launch. The eastern leg of the tour, which will start sometime in late spring, is still being finalized and will be announced soon.
Big Boy No. 4014 will be joined by two commemorative locomotives, including the railroad’s newest locomotive: No. 1776 – America250. This new commemorative locomotive pays tribute to the signing of the Declaration of Independence and the founding of the nation.
To be notified when news about Union Pacific’s legendary steam program becomes available, join the Official Union Pacific Steam Club at UP.com/SteamClub. Steam club members always get notified first when news about Union Pacific’s steam program is released.
Celebrate the Big Boy with Exclusive Merchandise
If you want to commemorate this historic tour with some merch, shop.trains.com has an impressive collection of Big Boy No. 4014 gear. Bring a piece of railroading history home, or bring it with you if you plan to attend any of the tour stops!
Union Pacific 4014 Spot Plate Pin, Big Boy 4014 Locomotive Pin, and Builder’s Plate Pin
These pins were designed to celebrate No. 4014’s restoration in 2019. They feature raised lettering, rubber backing for secure placement/wear, and silver hard enamel. Add them to your jacket, hat, bag or train memorabilia to give them some flair and start conversations.
Big Boy Chalk Writing Mug and Tee
These memorabilia items were designed exclusively for Trains magazine to celebrate the restoration and touring of Big Boy No. 4014, and now we’ll be excited to bring them to see the locomotive in person! Bring home these items yourself and you can rep your favorite magazine on the tour!
Union Pacific's Big Boys (Softcover)
Union Pacific's Big Boys: The complete story from history to restoration covers the who, what, why, and when of the 25 popular 4-8-8-4 steam locomotives. This book gives the historical background on the early 1940s development, explains why they were built, how they were used, and traces their history until they were retired in the 1950s.
This book also covers the much anticipated and well covered restoration of No. 4014 starting when it was recovered in a park in 2013 all the way through to its restoration and tour across the United States in the summer of 2019.
Visit shop.trains.com today to browse the complete collection of Big Boy No. 4014 merchandise and find the perfect way to celebrate this legendary locomotive.
- Written by Matt Herr