The living legend is traveling from its base in Wyoming -- on a heritage tour covering four states.
Number 844 was the last steam locomotive bought by Union Pacific.
"It was built in 1944. It's the second largest engine still running in the world, it's never been out of service," said Union Pacific conductor Reed Jackson
The steam train can go 120 miles an hour. The heritage tour will make stops in many cities that witnessed the birth of the railroad in the West.
The trip will take 32-days, and it wraps up in mid-May.