Union Pacific Railroad’s Big Boy No. 4014 recently whistled and puffed its way into Eastern Pennsylvania where the “world’s largest operating steam locomotive” has been booked for an extended stay through June 30 at Steamtown National Historic Site, 350 Cliff St., Scranton.

One of only eight remaining locomotives of this 4-8-8-4 configuration, No. 4014 will be displayed alongside Steamtown’s Big Boy No. 4012 as it receives routine maintenance. Both mammoth locomotives were built in 1941, among 25 manufactured exclusively for the Union Pacific Railroad over the course of World War II.

This Big Boy Reunion is part of a nationwide tour celebrating America’s 250th anniversary which began with a journey to the west coast from Big Boy No. 4014’s home at the UP Roundhouse in Cheyenne, Wyo., earlier this year. Retired in 1961 and reacquired from RailGiants Train Museum in Pomona, Calif., by Union Pacific, the historic loco was upgraded from a static display to a working UP ambassador that generally runs excursions once or twice a year.

Union Pacific’s design team, in partnership with American Locomotive Company (ALCO) in Schenectady, N.Y., developed the 4-8-8-4 locomotives to provide enough power to haul heavy freight and later troop trains, over the steep grades of the Wasatch Mountains in Utah and other tough western terrain. There are four pilot wheels, two sets of eight drivers, and a four-wheeled trailing truck to provide power and balance. Weighing 1.2 million pounds, and at 133 feet long, the frames are articulated (hinged), to allow these massive engines to negotiate curves.

Joining the thousands of tourists gathering outside of Steamtown were Bethlehem mom Janet Norris and her adult son Nate.

“I get it from my grandpa,” says the 24-year-old rail fan and modeler who still has the vintage Lionel electric train set gifted to him as a child.

An upstate New York family has strong ties to the two Big Boys. Visiting Scranton from Valley Falls, N.Y., were matriarch Bonny Collins, sons Edward, David and John H. Collins III, as well as daughters Carolyn and Barbara Collins. The 10-member entourage included two grandchildren and a nephew and his wife.

Bonny Collins was proud to share two photos her family brought with them of a freshly made Big Boy locomotive and the crew that built it in 1941. Her late father, Ernest Spigner, worked at ALCO and appears in both photos. Not only part of the crew that built these massive locomotives, Spigner is credited with coining the “Big Boy” nickname for them.

“This is No. 4000; this is the first one,” remarked Union Pacific Senior Manager of Steam Operations Ed Dickens as he was shown the photos. Pointing at No. 4014 which he operates, Dickens adds, “This is the 15th one.” Unfortunately, No. 4000 was scrapped in 1959 according to Dickens.

Seeing that John Collins III was wearing his grandfather’s ALCO company ID pin, Dickens explained that those pins were issued to defense industry employees at the time.

Several attendees expressed a calming sense of patriotism and unity with their fellow travelers as they made their way through the long lines. What appeared to be a bald eagle flew over the heads of people lined up for the souvenir tent, soaring past the pair of Big Boys.

While at Steamtown, visitors can also tour the Union Pacific Museum Experience railcar and view several historic passenger cars from UP’s Heritage Fleet, along with commemorative diesel engines honoring Abraham Lincoln and the America250 initiative that came along for the ride.

Having crossed the Midwest and made tracks into Pennsylvania in collaboration with Norfolk Southern, the refreshed No. 4014 will continue its coast-to-coast tour through Jim Thorpe on July 2, with short whistle stops at the Reading & Northern Outer Station, 3501 Pottsville Pike, Reading at 1:30 p.m., and at 51 South Hanover St., Pottstown at 3:30 p.m. Parking may be limited at these sites.

After passing through King of Prussia on July 3 with no scheduled public stops, Big Boy No. 4014 will be on exhibit at Intrepid Avenue and League Island Boulevard in Philadelphia from 9 a.m. - 3 p.m. July 4 - 5 to celebrate Independence Day. Starting July 6, Big Boy begins its return trip to Wyoming via Lebanon, Lewistown, Altoona and points west. For the full schedule and viewing guidelines, go to: up.com/about-us/history/steam/schedule.

“We sold 28,500 tickets today,” said Steamtown Superintendent Jeremy M. Komasz who estimates that around 30,000 showed up. “It’s a time-ticketed entry for the entire time Big Boy is here, so we can control the crowds.” At a cost of $1, they can be purchased at: nps.gov/steamtown

“We want everybody to have a great experience with the Big Boys,” says Komasz, “but also a great national park experience.”