FORT WORTH, Texas - The world's largest operating steam locomotive will be in Fort Worth through the weekend. Union Pacific's Big Boy No. 4014 will chug into Fort Worth to be on display Thursday.

The Union Pacific Big Boy No. 4014 is the world's largest operating steam locomotive. It will remain in Cowtown until Sunday, though it will not be on public display after Friday afternoon.

There are steam locomotives, and then there’s “Big Boy.” At 604 tons and 132 feet long and with a 4-8-8-4-wheel arrangement, it is the largest, most powerful steam locomotive in the world.

According to the Smithsonian, the National Museum of Transportation has "one of the largest and best ... one of the oldest steam locomotives in the U.S., the "Big Boy" #4006 Union Pacific Steam ...