The Largest Operating Steam Locomotive in the World Weighs 1.2 Million Pounds. Now, the Historic Train May Be Coming to Your Town

Built in the 1940s, Big Boy No. 4014 retired in 1961 after traveling for more than one million miles. It’s now making its way across the country in honor of America’s 250th birthday

Sonja Anderson | Daily Correspondent

July 13, 2026 1:26 p.m.

Share

Copy linkEmailSMSFacebookXRedditLinkedInBlueskyPrint

Add as preferred source

The world’s largest operating steam locomotive is currently chugging across the United States. It’s known as Big Boy No. 4014, and crowds of Americans are lining railroad tracks to watch it pass through their towns.

The locomotive stretches 133 feet long and weighs 1.2 million pounds. This month, it rolled through Valley Forge National Historical Park in Pennsylvania, “bells ringing and steam whistle blaring,” as NPR’s Jeff Lunden reports.

“It was pretty amazing,” spectator John Seibert, a member of a model railroad club, tells NPR. “When he blew the whistle right by us, it kind of went right through you. The sound went right through you.”

Big Boy is making a cross-country trip in honor of America’s 250th birthday, according to a statement from Union Pacific Railroad. After stopping in Philadelphia for July 4 and 5, it continued its long journey, which winds through Ohio, Indiana, Illinois, Missouri, Kansas and Colorado. At the end of the month, it will return home to Wyoming. Spectators can track the train’s movement online.

“It’s all manually operated; there’s nothing automatic,” train engineer Ed Dickens, senior manager of Union Pacific’s heritage operations, tells NPR. “Every sound, every move that it makes, is controlled by human hands. It’s just 1940s technology—very pure in that sense.”

As Big Boy traveled through western Pennsylvania on July 11, everyone inside the cab wore earplugs and eye protection, according to the Pittsburgh Tribune-Review’s Zachary Gibson. Because the furnace was so hot, workers made sure to drink water regularly. Hearing over the loud noise was also challenging, so they used hand signals to communicate.

This locomotive was one of 25 Big Boys that hauled supplies through the Wasatch Mountains, traveling between Utah and Wyoming. Designed by Union Pacific, they were constructed by the American Locomotive Company between 1941 and 1944.

The locomotives were “built for power,” according to the National Park Service. They were known as “Big Boys” due to their impressive weight and size. With extra wheels and larger cylinders, they were able to pull 120-car, 3,800-ton freight trains at 40 miles per hour.

Today, only eight of the Big Boys still exist. Most of them are on display in museums, but one is operational: No. 4014. The nearly 85-year-old locomotive retired from freight duty in December 1961, after traveling more than one million miles. In 2013, Union Pacific reacquired it from RailGiants Train Museum in California and began fixing it up.

Operating Big Boy: Inside the cab of America's most powerful steam engine

Watch on

“It’s kind of like the holy grail of all steam locomotive restorations,” said Austin Barker, lead journeyman machinist, in a 2014 post on Union Pacific’s website. “Bringing one back is an honor.”

In 2019, in honor of the first transcontinental railroad’s 150th anniversary, Big Boy No. 4014 returned to service. Now, the train is completing its “first-ever coast-to-coast journey,” says Union Pacific CEO Jim Vena in the statement.

“I think I can speak for all of us: It’s a trip of a lifetime,” Dickens tells CBS Pittsburgh’s Christopher DeRose and Madeline Bartos. “The crowds turning out for this locomotive are in the millions. And it’s just mile after mile of this heartwarming emotion that is just beautiful to see.”

Sonja Anderson | Read More

Sonja Anderson is a daily correspondent for Smithsonian magazine who covers art, archaeology and culture, from newly discovered artifacts to the latest art heists.