Train Basics ABCs Of Railroading Union Pacific Big Boy basics and frequently asked questions

Union Pacific Big Boy basics and frequently asked questions

By Jim Wrinn | August 3, 2021

Learn about the largest steam locomotive to roam the rails

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Union Pacific Big Boy basics

Steam locomotive with yellow passenger train in rolling hills
No. 4014 goes on tour in September 2019 as it climbs the hill at Speer, Wyo. Jim Wrinn photo

Q: Why is a diesel with Big Boy 4014?

A: The diesel serves many purposes. Its dynamic braking saves brake shoes. Its power provides a boost that saves on No. 4014 fuel stops. It’s a much-preferred power source in tunnels. And if Big Boy were disabled on the main line, the diesel could still move the train. In 2021, the diesel is also a part of the Positive Train Control safety system for No. 4014.

Q: What does Big Boy 4014 burn for fuel?
A: No. 4014 was built to burn coal but was modified to burn No. 5 fuel oil in 2019.

Steam locomotive generating clouds of steam on curve among trees
Big Boy No. 4014 rolls through Texas in November 2019. Jim Wrinn photo

Q: When will it make it to the East Coast?
A: It won’t. No. 4014 runs on the tracks the Union Pacific Railroad. The UP doesn’t go to the East Coast. In fact, the UP system basically stops at the Mississippi River with a few exceptions. The eastern-most tracks that UP runs are in Illinois and Louisiana. Key UP system eastern cities are Chicago, St. Louis, Memphis, and New Orleans. So, if you live in the East and want to see the Big Boy run, go west.

Q: What’s the steam coming out of the pipe under the cab?
A: The continuous flow under the right side of the cab is the discharge from one of two blowdowns. Originally, the valves were actuated by exhaust steam pressure, which means they operated only when the throttle was open. The large one up top was controlled by a system that was detecting the presence of foam in the steam space in the boiler foam trough. The railroad redesigned these so they can both be controlled from the cab using air pressure that is easily manipulated with two small air valves.

More Big Boy questions

Steam locomotive smoking lightly with yellow passenger train
Note the blowdown exhaust behind the cab at ballast level as the locomotive rolls through Texas in November 2019. Jim Wrinn photo

Q: Where do I get tickets to ride this?
A: Big Boy No. 4014 is on rolling exhibition when it is on tour. It does not pull regular public excursions. However, usually once a year, the locomotive pulls an excursion to benefit the nonprofit Union Pacific Museum in Council Bluffs, Iowa, from where the transcontinental railroad started west. The 2021 excursion is from New Orleans to Plaquemine, La. Details and ticket information are available at

Q: How fast can it go?
A: Big Boy was built to go as fast as 70 mph, but the locomotives rarely ran more than 50 mph, a speed the UP still finds convenient.

Q: How much can it pull?
A: With more than 6,000-horsepower, Alco and Union Pacific designed Big Boy to pull a 3,600-ton train across the mountains of Utah and Wyoming.

Q: Where can I see this one or one of the others?
A: Big Boy No. 4014 is not on regular display when it is in the UP-Steam Shop in Cheyenne, Wyo. The Cheyenne Depot Museum arranges occasional shop tours. The best place to see No. 4014 is on the road, and the current schedule is available from Union Pacific. As for the other survivors, you can find them easily.

Fence separates spectators from steaming and smoking steam locomotive on curve
Union Pacific Big Boy No. 4014 departs Marshall, Texas, in November 2019. Jim Wrinn photo

2 thoughts on “Union Pacific Big Boy basics and frequently asked questions

  1. With big boy’s basics and other frequently asked questions had those ask if 4014 is like any other mainline steam locomotive when a diesel locomotive is part of the consist for providing power for passenger coaches when the top reason the diesel is there to provide dynamic braking. In PTC territory the diesel is part of safety measures. Like any other mainline steam locomotive that was built to burn coal but after leaving the locomotive’s assembly plant or during a restoration to operating condition had it converted to burn fuel oil. Like any other articulated steam locomotive had ALCO and UP build the fleet of big boys to lift a 4,000 tone freight train out of a river valley or over a mountain.

  2. The last question, “Where can I see this one or one of the others?” was only answered in part.

    For those steam fans (particularly those east of the Mississippi River) wanting to see a Big Boy up close, no. 4012, one of the eight that were saved, is on display at Steamtown National Historic Park in Scranton, PA. It recently received a full cosmetic restoration, and is now back on display.

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