This is the largest and most powerful steam locomotive ever built...the Union Pacific Big Boy. This particular engine, 4014, was completely rebuilt and returned to full function in the last several years.
After rebuild, it made the trip to Promontory Summit for the 150th anniversary of the completion of the transcontinental railway. It then toured the nation for millions to see it up close and personal. Big Boy 4014 is one of only 8 Big Boys in existence, and the only working loco. It’s home base is Cheyenne, Wyoming.
There is another Big Boy in Cheyenne as well. Big Boy 4004 is set in a static display in Holliday Park, one mile east of the locomotive maintenance buildings for Union Pacific trains.
This image below was taken by me this past Wednesday. 4004 was retired in 1963 and donated to the city of Cheyenne. It and 4014, and the other 23 Big Boys were built specifically to haul heavy freight trains across the Rockies, from Cheyenne to Ogden, Utah.
4004 had only 441k miles on it when it left the rails. Basically, these two engines represent 1/4 of all existing Big Boys. 4014 now does excursion trips in the front range area, as well as trips to Salt Lake City.