Union Pacific’s “Big Boys” (1941 – 1944) 

In July 2026 the only operating Big Boy locomotive, the No. 4014, rolled through St. Louis and made a brief stop at our Museum, drawing a massive audience of fans.

The National Museum of Transportation is home to another Big Boy, No. 4006, which is on view in our extensive historic train collection! It had over 1,064,000 miles of service, the highest among all surviving.

Class 4000, known as Big Boys, consisted of twenty-five steam locomotives of the 4-8-8-4 configuration, ordered by the Union Pacific Railroad and built by the American Locomotive Company (ALCO) in Schenectady, NY, between 1941 and 1944.

All Big Boys were retired between 1959 and 1964. Currently, there are eight survivors, which can be seen displayed at different railroad museums in the United States, with 4014 still operational:

• 4004 Holliday Park in Cheyenne, WY
• 4005 Forney Transportation Museum, Denver CO
• 4006 The National Museum of Transportation, St. Louis, MO
• 4012 Steamtown National Historic Site, Scranton, PA
• 4014 Union Pacific Steam Shops, Cheyenne, WY (Or on tour!)
• 4017 National Railroad Museum, Green Bay, WI
• 4018 Museum of American Railroad, Frisco, TX
• 4023 Lauritzen Gardens, Omaha, NE