​​​In Search of Big Boys 

How one little boy's love of Thomas the Tank Engine led to a

country-wide search for really big steam engines.
























By Janet Wolfe
Posted June 22, 2026


     If you would have asked me 20 years ago if I could envision myself dedicating any of my free or vacation time to trains, I probably would have chuckled a little and said, “no.”

     But that was before we had kids.

     When he was just a toddler, our firstborn was captivated by the trains in the children’s shows Thomas & Friends and Chuggington.  Train shows led to train toys.  Train toys led to train books.  Train books led to booking his very first train ride, on a Thomas the Train-led excursion out of Baltimore, Maryland.

     The years that followed brought an equally train-enthusiastic little sister and more train “stuff.”  More Thomas train rides, Christmas train rides, steam-powered train rides, and rides on trolley cars.  Train yards, train museums, and model train displays.  An HO—then an O—scale train set under our Christmas tree.

     When we started taking road trips in 2018—even though the kids had outgrown Thomas and the toys—our family continued to incorporate train experiences in our activities, including riding the uniquely perilous Durango & Silverton in Durango, Colorado.

     And pursuing Big Boys.


What is a Big Boy?

     Commissioned by the Union Pacific Railroad and built in Schenectady, New York, by the American Locomotive Company (ALCO) between 1941 and 1944, “Big Boys” aren’t just large locomotives.  They are the largest steam engines ever built.  At almost 133 feet long—the height of an 11-story building—Big Boys take up nearly twice as much track as today’s freight engines, which typically measure 70 to 75 feet long.

     But it’s not just their size that makes them special.  These monstrous machines were also immensely powerful.  They did the work of three smaller engines, pulling heavy, World War II-related freight over the steep, mountainous terrain between Odgen, Utah, and Cheyenne, Wyoming.  Without helper engines.  Using only steam technology.  As a result, they were, and still are, considered icons of American engineering.

     As effective as they were, only 25 of these steam-powered locomotives were ever built.  Most of them were “really useful engines” for about 20 years before being replaced by more-efficient diesel locomotives.  Today, only eight Big Boys remain intact.  Only one is operational.


How Big Boys Got Their Start

     In 1940, life was pretty good for the Union Pacific Railroad.  Created in conjunction with the signing of the Pacific Railway Act of 1862, the company had enjoyed a rich 78-year history that included helping build America’s first transcontinental railroad, contributing significantly to the country’s western growth, aiding in the evolution of travel and trade, and becoming a key carrier in U.S. rail freight.

     But success didn’t come without challenges.  

     The Wasatch Mountains in Utah and Wyoming, one of the most demanding railroad routes in the country, was one of them.  Featuring long, steep climbs and narrow canyon passages, the Wasatch Mountains were hard on trains, often requiring the strength of two or three engines to pull heavy freight up and over them.

     In 1940, Union Pacific Railroad President, William Jeffers, decided there had to be a better solution.  He assigned Otto Jabelmann, Union Pacific’s VP of Research and Mechanical Standards, with a very specific task: design a freight engine that could pull more tonnage at more miles-per-hour than any engine in existence.  

     It took Jabelmann’s engineers and the designers at American Locomotive Company six months to tweak the Union Pacific team’s design and to acquire and fabricate parts.  It took another six months to build.  The result: massive engines that weighed 1.1 million pounds each, carried 33 tons of coal, held 24,000 gallons of water in its tender, and could pull a 3,600-ton train without help at speeds of up to 80 mph.

     How could something so big and heavy move so well?  What gave Big Boys their power?  A combination of their weight and wheel set.  In addition to their sheer heft, Big Boy engines sit atop a 4-8-8-4 wheel set.  All train engines have a set of four wheels in the front of the engine and four wheels in the back.  These wheels allow the engine to steer, and they support the front and back ends.  However, whereas traditional engines have two sets of six wheels in the middle for powered driving, Big Boys have two sets of eight wheels, which give them the traction and the power they needed for long mountain runs.

     And boy did they make long runs.  Of the original 20 Big Boys built in 1941, all of them logged more than 1,000,000 miles in their lifetimes.  The final five Big Boys, built in 1944, all logged 800,000+.


Why We Started Tracking Big Boys

     We didn’t actively seek out the Big Boys.  In fact, when we saw our first one—No. 4012—in 2011 on a visit to Steamtown National Historic Site in Scranton, Pennsylvania, we were there because it was on the way to upstate New York, where we were going to visit family.  

     We saw Big Boy No. 4017 in Green Bay, WI, in 2018 and No. 4006 in St. Louis, MO, in 2019 simply because they were located in cities we had already planned to travel to on our road trips.

     It wasn’t until 2021, when my husband realized that our road trip would take us to the right part of the country to see four more Big Boys, that we made a conscious decision to see them all. 


 Where You Can Find Big Boys Today

     If you have a train-lover, history-lover, or simply curious adventurer in your family and you’d like to see a Big Boy for yourselves, the good news is that most of the remaining eight are easily accessible.  The bad news is that they’re a bit spread out.  It took us 12 years and five different trips to see them all.  Still, if you can work a visit to even one of these bad boys into a road trip, you’ll get to see a rare piece of history.

Colorado:

  • No. 4005, Forney Transportation Museum, Denver, Colorado.  The 4005, built in September 1941, started its life like other Big Boys, burning coal.  In 1946, however, anticipating a coal disruption because of a strike, No. 4005 was converted to burn oil.  The 4005 operated this way until March of 1948, but because the design of the firebox didn’t allow the oil to burn hot enough to create enough steam pressure, the engine was converted back to coal-burning.  Five years later, tragedy struck when the engine was destroyed and several crew members killed following a devastating accident in Red Desert, Wyoming.  The engine was eventually repaired and returned to service, retired in 1962, and then donated, in 1970, to the Forney Museum, where you can find it displayed safely inside.


Missouri:

  • No. 4006, National Museum of Transportation, St. Louis, Missouri.  This train is displayed outside, and it is accessible to visitors: both of our kids got to stand inside the cab.  One of the original 20 ordered, Big Boy 4006 was built in 1941.  It ran its last run in 1959 but wasn’t officially retired until 1961.  This massive machine spent a year stored in the Alton & Southern Shops in East St. Louis before being donated to the National Museum of Transportation. Of all the Big Boys that existed, 4006 logged the most miles: 1,064,625. 


Nebraska:

  • No. 4023, Kenefick Park, Omaha, Nebraska.  Visible from Interstate 80 and accessible by parking at Lauritzen Gardens, the 4023 sits outside alongside Union Pacific’s Centennial class diesel-electric No. 6900.  Part of the second “batch” of Big Boys ordered (built in 1944), the 4023 was retired and donated in 1962.  Unlike the 4006 in Missouri, this Big Boy can be admired from the outside only.


Pennsylvania:

  • No. 4012, Steamtown National Historic Site, Scranton, Pennsylvania.  Like most of the other Big Boys, No. 4012 was built in 1941 and retired in 1962.  It didn’t sit idle for long as it was quickly obtained by F. Nelson Blount for display at his Bellows Falls, Vermont, museum.  In 1984, the 4012 was moved to Scranton and put on static display until 2019, when it underwent extensive cosmetic restoration that included replacing rusted parts, remediating hazardous materials, and receiving a new paint job.  Back on display at Steamtown in 2021, it is the only Big Boy to be found in the U.S.’s eastern time zone.


Texas:

  • No. 4018, Museum of the American Railroad, Frisco, Texas.  Built in 1941, the 4018 was retired in 1962 and donated and put on display in 1964.  The engine almost got a second life in 1998, when the museum was approached with a proposal to restore 4018 to operation for a feature film.  The movie opportunity never happened, but the engine can still be found on display, outside, for visitors to admire.


Wisconsin:

  • No. 4017, National Railroad Museum, Green Bay, Wisconsin.  This train is one of only two Big Boys kept inside, in a climate-controlled room.  The 4017 was built in 1941 and has been cared for and admired in Green Bay since its retirement in 1961.  Not only can visitors examine this Big Boy up close, but they can also step inside the cab (at least you could when we saw it in 2018).  


Wyoming:

  • No. 4004, Holliday Park, Cheyenne, Wyoming.  Free to see and easy to access in the southeast corner of Holliday Park at East 17th Street and Morrie Avenue, this Big Boy made its last run in 1958, was placed in storage, and officially retired in 1962.  In 1963, the 4004 was donated to the City of Cheyenne and moved to Holliday Park, where it sits on a concrete slab today, surrounded by a chain-link fence.  Parking is free and close.

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  • No. 4014, Union Pacific Railroad Steam Shop, Cheyenne, Wyoming.  Viewable from the sidewalk on the I-180 S overpass or by taking a steam shop tour through the Cheyenne Depot Museum, the 4014 is the only operational Big Boy in existence.  Retired in 1961, the 4014 was reacquired by the Union Pacific in 2013, restored, and returned to service in 2019, just in time for the 150th anniversary of the first transcontinental railroad.  


     Want to see a Big Boy in action?  In 2026, fans will have the unique experience of seeing Big Boy No. 4014 on the move as Union Pacific celebrates America's 250th birthday with a coast-to-coast tour.  The western leg of the tour began in Cheyenne, WY, on March 29 and travelled to Rock Springs, CA; Portola, CA; Roseville, CA; Elko, NV; Ogden, UT; and Evanston, WY, before returning to Cheyenne on April 24.   

     The eastern leg of the tour began on May 25 and includes stops in Omaha, NE; Chicago, IL; Buffalo, NY; Scranton, PA; Philadelphia, PA; Altoona, PA; Fostoria, OH; and St. Louis, MO.  For the complete schedule, visit https://www.up.com/about-us/history/steam/schedule.


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