The Union Pacific Big Boy was one of the largest and heaviest steam locomotives ever built. Weighing over 1,189,000 lb (539,000 kg), the engine produced 6,290 hp (4,690 kW) and could pull over 100 …
"The tender originally carried 56,000 lb (25,401 kg) of coal in a front compartment. In the late 1940s, 10 in (254 mm) tall steel sideboards were added to the top of the coal compartment. The sideboards enabled an additional 8,000 lb (3,629 kg) of coal to be loaded, increasing the tender’s capacity to 64,000 lb (29,030 kg). A rear compartment held 24,000 gallons (90,850 L) of water for the -1 class and 25,000 gallons (94,635 L) of water for the -2 class. At full steam, a Big Boy engine would consume the tender’s coal and water supply in two hours, but a proper facility could replenish the coal and water in eight minutes."
Before UP rebuilt 4014, their big locomotive was Challenger 3985, a 4-6-6-4. Big Boy 4014 is a 4-8-8-4. Here is a pretty impressive video of 3985 near Cheyenne, Wyoming. Unfortunately, 3985 is worn badly enough to need a total rebuild and has been retired.