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 world's largest operating steam locomotive - Union Pacific's Big Boy No. 4014 - rolled into and through Dallas in September and is back in Fort Worth in October.

A look at seven iconic trains that have shaped railroading, from luxurious passenger trains to high-speed record breakers.

Discover how CPR No. 2816 and UP No. 4014 fully embrace big steam and PTC, and reset the stage for other mainline locomotives ...

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 ...