Union Pacific Big Boy No. 4004 in Cheyenne, Wyoming
Outdoor rail parkFreeOutdoor display in Holliday Park
Big Boy No. 4004 is one of the 25 giant steam locomotives built for Union Pacific to haul heavy freight over the mountains without helper engines, and today it rests on public display in Cheyenne's Holliday Park.
- Built by ALCO in 1941
- One of 25 Big Boys
- 4-8-8-4 wheel arrangement
- Retired in 1962
- Outdoor park display
Union Pacific Big Boy No. 4004 at a glance
- Hours
- Outdoor park display; check with Visit Cheyenne for park hours
- Admission
- No admission fee posted for the park display
- Plan for
- About 20 to 30 minutes
- Best for
- Quick photo stop for families and steam fans
- Best ages
- All ages
Hours and prices as the museum posts them, checked October 19, 2026. Confirm before you go.
Look inside the book
Taking the kids to Union Pacific Big Boy No. 4004? Bring Rally along.
In Rally Takes the Train, a corgi's little legs can't manage the big train stairs, so Dad gives him a boost. It takes about five minutes to read, a good fit for the drive to Cheyenne.
Rally Takes the Train
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See who’s waiting at the station
Grandmommy and Papa are at the last stop. Get the full hand-painted book, $13.99 on Amazon.
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Built to haul freight over the mountains alone
When Union Pacific needed to conquer the Rocky Mountains, it turned to the Big Boy. Twenty-five of these engines were built exclusively for the railroad by the American Locomotive Company in Schenectady, New York, between 1941 and 1944. They were coal-fired articulated locomotives with a 4-8-8-4 wheel arrangement, designed to pull a 3,600-ton train up steep grades without the help of extra engines.
No. 4004 came out of the Schenectady plant in September 1941, early in the run. Railfan accounts say it was officially retired in February 1962 after running more than a million miles, and that it is the surviving Big Boy with the lowest number. Cheyenne's tourism bureau describes it as an imposing sight even in retirement. It now rests in Holliday Park, and a historical marker beside it tells the Big Boy story for anyone who stops.
A giant at rest in Holliday Park
This is an outdoor display: the locomotive sits in Holliday Park in Cheyenne, where families can walk around it and take in the size of a Big Boy from ground level. A historical marker nearby explains how the class was built. The display is not staffed, so pair it with the Cheyenne Depot Museum for the full story of why Cheyenne became home to the largest engines.
Don’t miss
- The 4-8-8-4 wheel arrangementTwo sets of eight driving wheels under one engine gave Big Boy the power to climb steep grades with a 3,600-ton train.
- The historical markerIt explains how ALCO built all 25 Big Boys for Union Pacific between 1941 and 1944.
- The view from the parkSeeing a Big Boy outdoors, with room to step back, is the best way to grasp just how long it is.
Feel tiny next to a Big Boy
Kids who have seen Big Boy in books get to stand next to a real one here, and the size alone does the teaching. Since the display is outdoors in a park, bring sun protection in summer and warm layers when the wind picks up. Visit Cheyenne does not post climbing rules, so follow any posted signs.
Plan your visit: tips for Union Pacific Big Boy No. 4004
- Pair it with the Cheyenne Depot Museum to learn why Cheyenne was Big Boy's base.
- Read the historical marker beside the engine before kids run off.
- Dress for the weather; there is no indoor space at the display.
- Watch for rare Steam Shop tours to see the operating Big Boy, 4014.
Shown off by the city and its visitors bureau
Visit Cheyenne, the city's convention and visitors bureau, promotes the Big Boy display along with Cheyenne's other railroad attractions. Its office can answer questions about the park and help with trip planning. Keeping the area tidy and following posted signs helps the engine stay in good shape for the next family.
From one Big Boy to the next
The Cheyenne Depot Museum tells the story behind the engine and is close by. The Union Pacific Steam Shop, home of Big Boy 4014, is about a mile away and opens only on tour days, and the Wyoming State Museum is about a mile off too. Find more on our Wyoming train museum guide.
- Cheyenne Depot MuseumCheyenne, WY · same town
- Wyoming State Museum railroad exhibitsCheyenne, WY · about 1 mi
- Union Pacific Steam Shop historic collectionCheyenne, WY · about 1 mi
- Historic Laramie Railroad DepotLaramie, WY · about 42 mi
- Colorado Model Railroad MuseumGreeley, CO · about 49 mi
- South Park Rail Society / Como RoundhouseComo, CO · about 71 mi
Bring Rally along: a train book for the drive
Big Boys were built to haul trains through the mountains, and mountains mean tunnels. In our book, the train rolls into a dark tunnel, and then comes a big bright light and happy cheers as it pops out the other side. Rally is snug between Mom and Dad the whole way. I picture a little one looking up at this giant and imagining that same rush. Our story page tells how the book began.
Free for train families
Print the Rally coloring pages before you go
Watercolor coloring pages from the book, free to print. Tuck a few in a folder with crayons for the drive or the wait for the next train.
Get the free coloring pages
A train story for the ride homeRally Takes the Train is a five-minute rhyming picture book about a corgi's first train trip to see his grand-paw-rents. Hand-painted in real watercolor. $13.99 on Amazon, for ages 0 to 8.
Buy on Amazon (opens in a new tab)More for train families
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- Train museums in every state: search by town or near you
- Christmas train rides in Wyoming
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- Every Amtrak route with kids
Work or volunteer at Union Pacific Big Boy No. 4004?
We want this page to be the best introduction to your museum on the web. Send new hours, event dates, corrections or photos to kelsey@rallytakesthetrain.com and we will update it. You are welcome to share this page with your members.
Sources
Everything on this page comes from the museum’s own website and social pages and, for history, Wikipedia, checked October 19, 2026.
Big Boy No. 4004 in Cheyenne: 20 quick answers
Where is Big Boy 4004 in Cheyenne?
Union Pacific Big Boy No. 4004 is on display in Holliday Park in Cheyenne, Wyoming. It is an outdoor display, and a historical marker beside the engine explains the Big Boy story. Visit Cheyenne, the city's visitors bureau, can help with directions and other railroad stops in town.
Is it free to see Big Boy 4004?
No admission fee is posted for the display. The locomotive sits outdoors in Holliday Park, a public park, so visitors can walk up and see it. Cheyenne's indoor railroad museum, the Cheyenne Depot Museum, does charge admission, but the park display itself is not listed with a ticket price.
When can you see Big Boy 4004?
Big Boy 4004 is an outdoor park display rather than a staffed museum. A railfan group lists it as viewable 24 hours a day, but daytime visits are best for seeing details and reading the marker. Check with Visit Cheyenne for current park hours or any work on the display.
What is a Big Boy locomotive?
Big Boys were coal-fired articulated steam locomotives with a 4-8-8-4 wheel arrangement, built so Union Pacific could pull a 3,600-ton train over steep mountain grades without helper engines. Twenty-five were built, all for Union Pacific, by the American Locomotive Company between 1941 and 1944.
When was Big Boy 4004 built?
No. 4004 was built in September 1941 at the Schenectady, New York plant of the American Locomotive Company, according to railfan records. It was part of the first group in a fleet of 25 Big Boys built for Union Pacific between 1941 and 1944.
When was Big Boy 4004 retired?
Railfan accounts say No. 4004 was officially retired in February 1962 after running more than a million miles in Union Pacific service. It was later placed on display in Cheyenne, where it has become one of the city's best-known railroad sights.
How many Big Boys were built?
Twenty-five Big Boys were built, all exclusively for Union Pacific, by the American Locomotive Company in Schenectady, New York, between 1941 and 1944. The historical marker beside No. 4004 in Holliday Park tells this story, so take a minute to read it with the kids.
How heavy a train could Big Boy pull?
Big Boys were designed to pull a 3,600-ton train over steep grades without helper engines. That was the reason Union Pacific ordered them: to move heavy freight through the mountains with fewer locomotives. Visit Cheyenne highlights this in its description of No. 4004.
Is Big Boy 4004 the same as Big Boy 4014?
No. Both are Union Pacific Big Boys connected to Cheyenne, but 4004 is the retired engine on display in Holliday Park, while 4014 is kept at Union Pacific's Steam Shop in Cheyenne. The shop opens to the public only on occasional tour days.
Can you climb on Big Boy 4004?
Visitor information does not mention climbing or cab access at the Holliday Park display. Follow any signs and fences posted at the engine. The display is meant to be seen from the ground, which is the best way to appreciate the locomotive's size.
How long should I spend at Big Boy 4004?
Twenty to thirty minutes is enough to walk around the engine, read the historical marker and take photos. Combine it with the Cheyenne Depot Museum and, if you are lucky with timing, a Union Pacific Steam Shop tour for a full Cheyenne railroad day.
Is Big Boy 4004 good for kids?
Yes. It is free, outdoors and quick, so even toddlers can enjoy a short stop. Kids are usually amazed by the size of the wheels and the length of the engine. Bring sunscreen or warm layers depending on the season, since there is no shelter at the display.
Who built Big Boy 4004?
The American Locomotive Company, known as ALCO, built No. 4004 at its plant in Schenectady, New York. ALCO built all 25 Big Boys exclusively for Union Pacific. Railfan records list 4004's construction number as 69575.
Why is a Big Boy in Cheyenne?
Cheyenne was a key Union Pacific city, and the railroad's Big Boys worked the mountain routes in the region. Visit Cheyenne promotes No. 4004 as part of a cluster of railroad attractions that also includes the Cheyenne Depot Museum's exhibits and its model railroad.
Is there a historical marker at Big Boy 4004?
Yes. A historical marker titled Cheyenne's Big Boy 4004 stands at the display. It notes that 25 Big Boys, called the world's largest steam engines, were built only for Union Pacific by the American Locomotive Company in Schenectady between 1941 and 1944.
Is there parking near Big Boy 4004?
Visit Cheyenne does not list parking details for the display. Holliday Park is a city park, so look for park or street parking nearby. Call Visit Cheyenne's office if you are traveling in an RV or with a large group and need advice.
What other old steam engine can I see in Cheyenne?
Visit Cheyenne also points visitors to Engine 1242, which it calls Wyoming's oldest steam engine. For the full railroad picture, the Cheyenne Depot Museum covers the transcontinental railroad and Cheyenne's role as the base for the biggest locomotives.
Can you see Big Boy in winter?
Yes, the display is outdoors year-round, though Cheyenne winters can be cold and windy. Bundle up and plan a short stop, then warm up at the Cheyenne Depot Museum, which keeps regular hours seven days a week.
Who looks after the Big Boy 4004 display?
The engine sits in Holliday Park, and Visit Cheyenne, the city's convention and visitors bureau, promotes it as one of Cheyenne's railroad attractions. For questions about the display or the park, contact Visit Cheyenne through cheyenne.org.
What train museums are near Big Boy 4004?
The Cheyenne Depot Museum is close by, and the Wyoming State Museum and Union Pacific Steam Shop are each about a mile away. The Historic Laramie Railroad Depot is about 42 miles west, and the Colorado Model Railroad Museum in Greeley is about 49 miles south.
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