After nearly 60 years off the tracks, the world’s largest steam locomotive roars

(CNN) — With plumes of smoke billowing into the sky, the world’s largest steam locomotive left Wisconsin on Friday morning, bound for an afternoon stop in West Chicago.

Back on the rails for the first time in six decades, the only operational Big Boy steam engine in the world is on a journey across the Midwest to mark the 150th anniversary of the completion of the Transcontinental Railroad in 1869.

After logging more than 1 million miles on Western railroads, engine No. 4014 was retired in 1961 and given to a chapter of the Railway and Locomotive Historical Society in Southern California.

Union Pacific engineers have been doing restoration work on 4014 for the past two years in Cheyenne, Wyoming.

The steam engine stopped Tuesday in Altoona, Wisconsin, about 90 miles east of Minneapolis. Thousands gathered to take in the sight.

Union Pacific’s historic Big Boy steam locomotive No. 4014 rounds a bend outside Nevada, Iowa.

Jim Mone/AP

By August 2, the train will be in Omaha, Nebraska, for the weekend, and it’ll spend the first half of the week making stops in Nebraska on the way back to its original perch at the Union Pacific Steam Shop in Cheyenne on the morning of August 8.