The biggest steam locomotive is whistle-stopping across the U.S.

Attendees take photographs and admire Union Pacific’s Big Boy No. 4014, the world’s largest operating steam engine locomotive, during a stop in Philadelphia on July 5, 2026. As part of the celebration for America’s 250th anniversary, the steam engine train is on tour for public display in multiple cities and states across the United States.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

Union Pacific Railroad’s Big Boy No. 4014– the world’s largest operating steam locomotive – has been barnstorming from coast-to-coast in a celebration of America’s 250^th birthday. Based in Wyoming, the train came east to Philadelphia for the July 4^th weekend.

On the hottest day of the year – 102 degrees with a heat index that made it feel like 112 – dozens of people camped out by the side of the tracks at Valley Forge National Historical Park to see the train steam by. Many people brought camp chairs and coolers with water, like John Seibert, who came with a couple of friends from a model railroad club.

“It’s a once-in-a lifetime experience,” he said, “I mean you’re never gonna see it again.”

Many in the crowd checked their smartphones to see the progress of the train on an app, as it made its way down the track. And from miles away, you could hear the whistle. Then, the crowd could see the headlights in the distance. Then the Big Boy, 133 feet long and weighing 1.2 million pounds, came barreling past, bells ringing and steam whistle blaring.

Adam Lapham, 25, of Green, Ohio, stands for a photograph taken by his grandfather, James Wallace, 74, in front of a train car connected to Union Pacific’s Big Boy No. 4014, the world’s largest operating steam engine locomotive, during a stop in Philadelphia.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

“It was pretty amazing,” exclaimed Seibert. “When he blew the whistle right by us, it kind of went right through you.”

A few days later, engine 4014, and the 18-car long Union Pacific train it pulled, parked in Philadelphia’s Navy Yard, where crowds could get up close and personal. Fifteen-year-old Brandon Westerfield of Leonardo, New Jersey, came with his mother.

“I mean it’s obvious, but it’s huge,” said the young train enthusiast. “It’s so cool to see just something that big right in front of you.”

Union Pacific’s Big Boy No. 4014, the world’s largest operating steam engine locomotive, is seen during a stop in Philadelphia, Pennsylvania on Sunday, July 5, 2026. As part of the celebration for America’s 250th anniversary, the steam engine train was on tour for public display in multiple cities and states across the United States.

Union Pacific’s Big Boy No. 4014, the world’s largest operating steam engine locomotive, is seen during a stop in Philadelphia.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

Train enthusiast Brandon Westerfield, 15, stands for a portrait with his mom, Alethea Westerfield, 47, in front of Union Pacific’s Big Boy No. 4014.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

His mother, Althea, who has seen many trains with her son, said: “When he told me about it, I was like, okay, it’s another train, but now that I’m here, this is absolutely incredible. I’ve never seen such a sight.”

A train and its celebrity

The Union Pacific Railroad Company ordered twenty-five Big Boy locomotives, from 1941 to 1944, to haul freight through the Wasatch Mountains in Utah and Wyoming. The engines had an articulated design, to allow them to take curves, and two sets of pistons, driving eight wheels each. The last Big Boy retired in 1962 – they were all replaced by diesel engines.

Ed Dickens, the senior manager of Union Pacific Heritage Operations, looks out to the crowd of attendees from Union Pacific’s Big Boy No. 4014, the world’s largest operating steam engine locomotive, during a stop in Philadelphia. Dickens is the head the steam program at Union Pacific, and was responsible for the leading the team to restore Big Boy No. 4014.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

A detail of Union Pacific Locomotive No. 1616, a commemorative train car honoring President Abraham Lincoln, is seen connected to Union Pacific’s Big Boy No. 4014.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

Eight of these behemoths were preserved, but only one – number 4014 – is in operating condition. The restoration of the engine was overseen by Ed Dickens, senior manager of Union Pacific’s Heritage Operations. He’s also the train’s engineer.

Dickens is straight out of central casting, with his overalls and cap with the Big Boy’s number on it. He’s usually the guy at the throttle of this 7000-horsepower beast, as it hauls the train across the country.

“It’s all manually operated, there’s nothing automatic,” Dickens explained, after a round of selfies with fans of the Big Boy.

Ed Dickens, the senior manager of Union Pacific Heritage Operations, is seen speaking during an interview during a stop for the Union Pacific Big Boy No. 4014 in Philadelphia.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

Joe Stefankiewicz, 37, of Aston, Pennsylvania, holds a signed model train car for his son, Joey, 5, in front of Union Pacific’s Big Boy No. 4014, the world’s largest operating steam engine locomotive, during a stop in Philadelphia.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

“Ed Dickens is just a super ambassador,” said Matt Zollers, who came from Hatsboro, PA, to see the Big Boy. “What a great guy, great representative of the Union Pacific. Takes his time to talk to everyone, so friendly, so shout out to him.”

An attendee wears a t-shirt commemorating Union Pacific’s Big Boy No. 4014.

Michelle Gustafson for NPR

Michelle Gustafson for NPR

“From a personal standpoint, seeing the happiness, seeing the crowds is something that’s just spectacular for us,” Dickens said, standing in front of the engine.

Over two days, close to 100,000 people visited the Big Boy in Philadelphia. But all too soon, it departed on its way back home to Wyoming. It’ll have stops in Pennsylvania, Ohio, Illinois, Missouri, Kansas and Colorado along the way.

Dickens had a word about safety for folks who want to catch it, as it passes by their towns: “Please don’t hesitate to tell your fellow Americans, ‘Hey people, I talked to the train engineer and he told me to tell you to stand back. Always 25 feet back.'”

And, if not, the Big Boy’s whistle will most certainly warn them.

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