Here's how to see Big Boy, the world's largest steam locomotive, in western Pennsylvania

The historic Big Boy No. 4014, the world's largest operating steam locomotive, is rolling through western Pennsylvania on Saturday, ending with a stop in Leetsdale. 

Called the "Elvis Presley" of steam locomotives, the legendary Union Pacific Big Boy No. 4014 has been crossing the country to celebrate America's 250th birthday. It celebrated the Fourth of July in Philadelphia, and now it's coming back through the Pittsburgh area before making its way back home west.

Where will Big Boy stop in Western Pennsylvania? 

Big Boy will stop in Leetsdale on Saturday at 6:15 p.m. Before then, it will roll through multiple other communities. 

According to both Union Pacific and train experts KDKA consulted with, the tentative Saturday, July 11, schedule is as follows:

• 9 a.m. - Leaves Altoona
• 9:30 a.m.-10 a.m. - Stop at Horseshoe Curve National Historic Site
• 10:45 a.m.-11:15 a.m. - Stop in Cresson, Pennsylvania
• About 1:30 p.m. - Roll through Derry, Pennsylvania
• About 1:35 p.m. - Roll through Bradenville, Pennsylvania
• About 1:45 p.m. - Roll through Latrobe, Pennsylvania
• About 2:15 p.m. - Roll through Greensburg, Pennsylvania
• About 2:35 p.m. - Roll through Jeannette, Pennsylvania
• Time TBD - Roll through South Side Flats/Station Square along the Monongahela River. Big Boy will cross the Ohio River on the bridge over Brunot Island.
• 6:15 p.m.-6:45 p.m. - Stop in Leetsdale, Pennsylvania. From the Borough of Leetsdale: the viewing location for Big Boy will be at Ferry Street Railroad Crossing near the Subway.

Other times and locations for roll-throughs have not been determined yet. 

And while Union Pacific wants everyone to come out and see the Big Boy, they want everyone to be safe. They're reminding people to stay 25 feet off the tracks and never cross or put anything on the tracks, especially when the Big Boy is rolling through.

What is Big Boy No. 4014?

Built in 1941 to haul massive military and freight loads over the Wasatch Mountains during World War II, the Big Boy was one of just 25 locomotives ever built.

"It is just an astounding piece of machinery," Ian Luconti from Friendship, Pennsylvania, said while seeing Big Boy in Altoona. "I don't know how somebody could wake up one day and say, 'I'm going to build a steam engine.' I just wanted to come and see it. It's historic, there's only a couple of them in the world that I know of."

Today, only eight others survive on display across the country. But after a years-long restoration led by engineer Ed Dickens and his crew, Big Boy No. 4014 is the only one still under steam and operating on America's rails.

"It brings people together," Dickens said. "It brings communities together, it brings everyone together, and it's brought our companies together in a way that is necessary to do this and it is a lot to pull off."

And just how big is the Big Boy? It carries about 25,000 gallons of water, weighs roughly 1.2 million pounds, and stretches 133 feet from end to end — nearly 60 feet longer than a typical diesel locomotive, making it the largest operating steam locomotive in the world.

As part of America's 250th anniversary, Big Boy No. 4014 has been on a coast-to-coast tour, crossing the Mississippi River and into the Ohio Valley for the first time since it was built in New York in 1941. Thousands of people gathered to watch it in Erie County when it came to Pennsylvania for the first time. 

"I think I can speak for all of us: it's a trip of a lifetime," said Dickens. "And we are people that are accustomed to seeing large crowds turning out for the Big Boy. 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."