The Union Pacific 4014 Big Boy Steam Locomotive pulls into Kirkwood, Mo., on August 2021. It is similar to the Santa Fe 3751 steam locomotive that will be on display at this year's train festival ...

Union Pacific's Big Boy No. 4014 locomotive train visits and whistle stops at Greeley, Denver, Cheyenne for limited summer 2025 tour with No. 1616 Locomotive.

The world's largest operating steam train is in Denver. Union Pacific's legendary Big Boy No. 4014 locomotive made a pit stop in the Mile High City on Friday.