Receive the daily Popular Science newsletter💡 Breakthroughs, discoveries and DIY tips delivered six days a week. By registering, you confirm that you are over 16 years of age, will receive newsletters and promotional content, agree to our Terms of Use, and acknowledge the data practices in our Privacy Policy. You can unsubscribe at any time.
There’s still time to see Big Boy, also known as the world’s largest operating steam locomotive, before it concludes its first coast-to-coast run. Union Pacific’s Big Boy No. 4014 still has stops scheduled in Ohio, Indiana, Illinois, Missouri, Kansas, Colorado and Wyoming before the end of July.
Those who can’t make it to the heart of the country to see the locomotive can follow its progress with an online tracker. Union Pacific and Norfolk Southern tracks are marked in red. Big Boy’s expected route (subject to change) is highlighted in yellow.
The first leg of the steam train tour to celebrate the 250th anniversary of the United States began on March 29. Big Boy and other historic passenger cars from Union Pacific’s Heritage Fleet will travel from the locomotive’s base in Cheyenne, Wyoming, west toward California. Since then, it has made stops across the country, including parts of California, Utah and New York.
Big Boy celebrated the Fourth of July in Philadelphia, Pennsylvania, where the Declaration of Independence was written in 1776. Thousands of train enthusiasts braved temperatures of 102 degrees Fahrenheit (with a real feeling of 112 degrees) to catch a glimpse of the 133-foot-long, 1.2 million-pound train.
“This country was built on things like this. And I think it’s great to see things like this. It’s been restored,” an unidentified Big Boy fan told NBC 10.
Big Boy No. 4014 is currently the largest operating steam locomotive in the world. The train is one of eight remaining Big Boys and the only one still in operation. A total of 25 Big Boys were ordered for the Union Pacific Railroad with the first being first delivered in 1941. These powerful locomotives were built to haul heavy equipment to support the war effort.
Given their length, the train frames are “hinged” to help them negotiate curves. The Big Boys also have a 4-8-8-4 wheel arrangement. There are four wheels in the main set of “pilot” wheels that guide the engine; eight drivers are in the first engine; an additional set of eight drivers is on the second engine; and four wheels behind to help support the rear of the locomotive.
In the mid-20th century, the Big Boys typically moved approximately 430 miles between Ogden, Utah, and Cheyenne, Wyoming. Big Boy No. 4014 was officially retired in December 1961 after traveling 1,031,205 miles.
2025 PopSci Best of what’s new
Keep following us for the latest insights.
