Referred to as an "articulated" locomotive, because it has more than one set of drivers, Big Boy weighs 1,250,000 pounds (570,000 kg).

This locomotive worked for 21 years hauling freight between Cheyenne, Wyoming, and Ogden, Utah, logging over 1,000,000 miles (1,600,000 km) before its retirement in 1962.

[2] The Big Boy was on display at Bellows Falls, Vermont, until 1984, when Steamtown moved to Scranton, Pennsylvania.

[1] Since the Steamtown turntable and roundhouse are too small to accommodate the size and weight of 4012,[1] it has remained outdoors since its arrival at Scranton.

However, the study also recommended that 4012 remain on static display, because it is doubtful that the "track, switches, culverts, trestles, bridges, wyes, turntables, and other facilities that would have to carry it [could] bear its great weight".