The 25 'Big Boys' were built to pull long, fast freight trains over the Wasatch Mountains of Utah and Sherman Hill in Wyoming. They served there until 1959 when the new diesel-electric locomotives took over. 'Big Boy' #4012 was retired by the Union Pacific in 1962, when F. Nelson Blount obtained it for display at his former Bellows Falls, Vermont, museum. It was displayed, non-operative, there until 1984 when it was moved to Scranton, Pennsylvania. The 'Big Boys' were not the most powerful engines, though they were the heaviest. But no engine ever came close to matching 'Big Boy's' combination of speed, power and agility. Today, the Union Pacific 'Big Boy' #4012 is preserved and on display at Steamtown. Though it remains non-operative, it remains a most impressive machine.