The Union Pacific 4014 Big Boy Steam Locomotive attracted hundreds of visitors as it stopped in downtown St. Louis and Kirkwood, Missouri, U.S. on August 29 and 30. /CFP

Nearly 40 meters long and weighing 560 tonnes, the Big Boy is generally accepted as the world's largest steam locomotive, according to the Guinness Book of World Records. /CFP

The giant locomotive is on a five-week tour that includes public display events in five major cities, along with brief whistle-stops in more than 90 other communities in 10 states. /CFP

Starting earlier in the month in Texas, the locomotive will end its tour in Wyoming. /CFP