The Mighty Big Boy steam locomotive number 4004 in Cheyenne in Wyoming was one of 25 Big Boy locomotives that were built exclusively for Union Pacific Railroad by the American Locomotive Company in Schenectady in New York between 1941 and 1944 at a cost of greater than a quarter of a million dollars for each one.
The Mighty Big Boy Locomotive 4004 in Cheyenne in Wyoming
Big Boys are the largest steam engines in the world, as each locomotive weighed 1.2 million pounds and was 132 feet in length. Because of their great length, the frames of the Big Boys were “hinged” — or articulated — to allow them to navigate curves.
During construction of the first engine, a worker chalked the words “Big Boy” on the smoke box door; and the nickname was adopted. The massive engines primarily operated on the rugged run between Cheyenne and Ogden in Utah.
The final run of Big Boy number 4004 steam locomotive was on Friday, October 31, 1958 as it traveled from Cheyenne to Laramie, where it was retired from service. It was stored for a few years in Laramie before it was donated to the city of Cheyenne. The 4004 was moved to Holliday Park on Friday, June 28, 1963 on 600 feet of temporary track connecting the park with Union Pacific’s track.
Big Boy number 4004 is one of eight surviving examples of the largest steam locomotives in the world which are on display. It ran between Cheyenne and Ogden, Utah. It ran for 440,545 miles before it was retired from service.
Final Boarding Call
I did not know about the Big Boy Number 4014 Coast-to-Coast tour across the United States in celebration of 250 years since this country was founded — and even though this steam locomotive is also based in Cheyenne, it had already departed on its tour by the time I visited this capital city in Wyoming. I would have liked to have seen that locomotive in action…
…but if you are unable to see the Big Boy number 4014 steam locomotive as it treks back across the United States to Cheyenne, you can still see the Big Boy number 4004 steam locomotive in Holliday Park, where it has been stationary in the same spot for greater than 63 years.
Big Boy 4004 Locomotive
Holliday Park
1705 Morrie Avenue
Cheyenne, Wyoming 82001
United States
1-307-637-6423
info@cheyenne.org
No admission is charged to visit Big Boy Locomotive number 4004; the site is never closed; and plenty of free parking is available in the park.
All photographs ©2026 by Brian Cohen.
