Union Pacific #4012

Union Pacific #4012 "Big Boy" black steam locomotive with grey smokebox
Union Pacific #4012 4-8-8-4 "Big Boy" steam locomotive on static display at Steamtown NHS

NPS Photo

Union Pacific #4012

4-8-8-4, Builder: American Locomotive Works (Schenectady, NY) November 1941
Builder's No. 69583
Cylinders: 23-3/4 inch diameter, 32-inch stroke
Drive Wheels: 68-inch diameter
Weight on Drivers: 540,000 lbs
Boiler Pressure: 300 lbs
Maximum Tractive Effort: 135,375 lbs

Built for the Union Pacific Railroad as one of twenty-five 4-8-8-4 ("Big Boy") steam locomotives ordered by the UP to haul heavy freight across the Continental Divide. Big Boys are famous as among the most powerful steam locomotives ever built. Weighs 1,200,000 pounds. Front set of drive wheels are articulated to move freely around sharp curves. Four cylinders, tractive effort equals four lesser locomotives, built to achieve 80 mph speeds. One of eight remaining of this classification.

Last updated: September 28, 2017

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