: The frame is "hinged" to navigate tight curves.

The (4000-class) is the largest and heaviest reciprocating steam locomotive ever built, designed specifically to haul massive freight trains over the steep Wasatch Mountains in Utah and Wyoming. Key Features and Specifications

: Features 4 leading, 16 driving, and 4 trailing wheels for immense traction.

: Generates over 7,000 HP, measures over 132 feet long, and weighs more than 1.2 million pounds.

The Big Boy is a marvel of 1940s engineering, built to a scale that remains unmatched by other steam locomotives.