Many residents of Altoona likely awoke Wednesday morning to a blaring whistle that signaled the end of a historic visit to the city.

Union Pacific’s Big Boy No. 4014 — the world’s largest operating steam locomotive — visited Altoona on Tuesday for a celebration that included much fanfare and spent the night before thundering through other parts of Wisconsin. A lengthy stop in West Chicago was slated to begin Friday.

A gala celebrating the locomotive’s local appearance left an impression not only on spectators but the train’s operators. Engineer Ed Dickens said no crowd on the train’s tour — which commemorates the 150th anniversary of the transcontinental railroad’s completion — seemed larger than the one that welcomed it to Altoona.

“It’s humbling and heartwarming to see all these people turn out and to see the expressions on their faces,” he told the Leader-Telegram’s Eric Lindquist. “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.”

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At 133 feet, Big Boy No. 4014 is more than three times longer than a school bus and less than 100 feet shorter than a Boring 747 airplane. Big Boy is 17 feet tall and weighs in at about 1.2 million pounds.

“Just the sheer size of it is amazing,” Altoona Mayor Brendan Pratt told Lindquist. “It’s massive.”

Added Gary Miller, a 71-year-old train enthusiast from Eau Claire: “Oh man, it’s just beyond description. I can’t get enough of it. It’s a pretty special thing for this to be in Altoona, Wisconsin, and for us to be able to see it in person.”

Altoona officials had expected anywhere from 1,000 to 5,000 people at the event. One police officer at the event estimated that the crowd exceeded 10,000.

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Twenty-five Big Boys were produced for Union Pacific and in their heyday they typically operated between Cheyenne, Wyo., and Ogden, Utah. A worker on one of the units under construction wrote “Big Boy” in chalk on the train and the name caught on.

Big Boy No. 4014 traveled more than 1 million miles over 20 years before being retired in 1961. It recently underwent more than two years of restoration work. According to an article in Popular Mechanics magazine, the project required a team of nine full-time employees.

“We’re very, very excited and glad they selected Altoona as their only overnight stop in Wisconsin,” Mike Golat, Altoona city administrator, told Lindquist before the celebration. “We are and always have been a railroad town.”

The roughly three-week tour is scheduled to end in Cheyenne on Aug. 8.

“It’s about being able to show it to the people,” Dickens said. “That whistle speaks to people.”

It certainly did in Altoona.

Liam Marlaire, assistant editor