4-8-8-4 Class 4000 'Big Boy' UP Profile and Models

The Union Pacific "Big Boy" is a class of articulated 4-8-84 steam locomotive, produced in the early 1940s. 25 of these huge locomotives were built to haul long freight services over the Wasatch Mountains between Utah and Wyoming and were later seen on workings over Sherman Hill. They were the only locomotives to use the unusual 4-8-8-4 wheel arrangement and features a huge 150 sq ft firebox. No. 4014 was reacquired by the Union Pacific in 2013 and has been completely restored to operational condition, which included converting it to run on oil. The locomotive has been seen touring the Mid-West throughout Mid-2019 as it regained its title as the largest, heaviest and most powerful operating steam locomotive in the world.

(Information provided by Wikipedia)

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Surviving Examples