ALTOONA — Thousands of people from across the Midwest made their way to Altoona on July 23 to catch a glimpse of something many of them never thought they’d see: a working steam locomotive.

Not just any steam locomotive, but the world’s largest operating steam locomotive.

Union Pacific’s 133-foot-long Big Boy No. 4014 roared into town, steam flying and whistle blowing, a little ahead of its scheduled 1 p.m. arrival time to cheering crowds and even a few tears of joy.

The visit was part of a tour of the Midwest by Union Pacific to celebrate the 150th anniversary of the golden spike that completed the nation’s transcontinental railroad. While the locomotive was scheduled to make 15- to 45-minute “whistle-stops” in Superior, Baldwin, Merrillan, Warrens, Adams, Friesland and Butler, Altoona was the only Wisconsin city to land a longer stay with public display.

Engineer Ed Dickens said the restored engine, the only operating Big Boy locomotive remaining of the 25 ever built, has been attracting big crowds throughout its tour, but none seemed larger than what the steam crew witnessed upon arrival in Altoona.

“It’s humbling and heartwarming to see all these people turn out and to see the expressions on their faces,” said Dickens, Union Pacific’s manager of heritage equipment and one of the people involved in Union Pacific’s two-year renovation of Big Boy No. 4014. “When we arrived and I got down on the ground, a lady told me just seeing the train made her feel emotional because it reminded her of her father and grandfather, and then she broke down crying.”

The rail yard and the part of downtown near where the 17-foot-tall engine was parked, occasionally blaring a whistle that could be heard for miles, was crawling with people gawking at the big black machine, posing for photos in front of it and trying to get the best vantage point for photos and videos.

Jenni Sheteron brought her three children, Miles, 7, Mason, 5, and Addi, 4, all the way from Milwaukee to see the train, in part because Mason loves trains.

It didn’t disappoint, as Mason said it was even bigger than he thought, after posing with his siblings for a photo next to one of No. 4014’s wheels that was more than twice his height.

Altoona Mayor Brendan Pratt was thrilled by the reception given to the Big Boy and noted the event was a perfect fit for a town founded as a railroad terminal. He also was personally impressed by the locomotive that attracted all those people.

“Just the sheer size of it is amazing. It’s massive,” Pratt said.

City officials acknowledged they didn’t know what size crowd to expect and said it was nearly impossible to estimate the number of people in attendance at an event spread out around downtown and lasting several hours. At times traffic was backed up as far as the eye could see at several intersections, and one Altoona police officer said the crowd must have numbered at least 10,000.

Visitors also lined up to tour the Experience the Union Pacific Rail Car — a free traveling exhibit about railroad history and technology.

The Altoona stop drew passionate responses from many visitors, some who love anything to do with trains and some who were simply curious about seeing a slice of American history.

David Wiedenkeller’s love for steam locomotives was evident at a glance, as he wore a Big Boy No. 4014 cap and T-shirt he had purchased online before making the drive from his home in Racine.

Wiedenkeller, a railroad enthusiast his whole life, said he has been following the engine’s progress online as it tours the country and planned to visit Altoona as soon as he learned it would be the train’s only extended stop in Wisconsin. He is equally excited to take photos as the train goes through Racine later in the week. “It literally will go right by my house,” he said with a grin.

“There is is something mesmerizing about a steam locomotive,” he said. “You can see it all moving, almost like it’s a living thing.”

At a time of increasing political polarization in the U.S., trains have the potential to bring people together, said Wiedenkeller, who gives lectures about the history of steam locomotives and is even writing a children’s book titled “Old Smoky Comes Home,” inspired by his personal story, about a boy’s love of toy trains.

“This Big Boy is a symbol of American pride and American ingenuity,” Wiedenkeller said, adding that the engines were created to haul military supplies during World War II.

Big Boy No. 4014 was delivered to Union Pacific in December 1941 and traveled 1.03 million miles before being retired in December 1961.

Gary Miller, a 71-year-old train buff from Eau Claire, said somehow the locomotive’s visit escaped him until that morning when he received messages from several friends.

“I dropped everything and came over right away,” Miller said. “The first thing I did is I went out to the nose and kind of hugged it.”

Miller has been enthralled with trains since he was a boy growing up in Crystal Falls, Mich., where trains carrying iron ore would rumble right by his family’s house.

“As the trains came by, the whole house would shake, pictures would fall off the walls and glasses would slide off the table, and I couldn’t figure it out because everybody would clap and cheer even though stuff was breaking,” he said. “But it meant that my dad and his nine brothers all had jobs working in the mines.”

With that background, Miller wasn’t about to miss a chance to see a working steam locomotive right in the Chippewa Valley.

“Oh man, it’s just beyond description. I can’t get enough of it,” said Miller, who is in the market for a new home in the Eau Claire area with only one prerequisite — it has to be close to the railroad tracks.

“It’s a pretty special thing for this to be in Altoona, Wisconsin, and for us to be able to see it in person,” Miller said.

Dickens, who has seen such enthusiasm everywhere Big Boy No. 4014 has stopped, said that’s the reason Union Pacific officials chose to invest in the renovation.

“It’s about being able to show it to the people,” said Dickens, sporting the traditional denim overalls of a railroad engineer. “That whistle speaks to people.”