Union Pacific 4012

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Union Pacific 4012
Union Pacific 4012 Big Boy Steam Locomotive.jpg
"Big Boy" 4012 on static display at Steamtown National Historic Site
Type and origin
Power type Steam
Builder American Locomotive Company
Serial number 69583
Build date November 1941
Gauge 4 ft 8 12 in (1,435 mm)
Fuel type Coal
Operators Union Pacific Railroad
Class 4884-1
Numbers 4012
First run 1941
Last run 1962
Disposition Static display at Steamtown National Historic Site

Union Pacific 4012 is one of the world's largest steam locomotives and is one of eight preserved Union Pacific Big Boy locomotives. Built by American Locomotive Company in November 1941, Big Boy 4012 was retired in 1962 and can be viewed at Steamtown National Historic Site in Scranton, Pennsylvania.


Union Pacific 4012, nicknamed "Big Boy", is a 4-8-8-4 type locomotive built by American Locomotive Company in November 1941. It is among the world's largest steam locomotives. One of 25 built, No. 4012 is one of eight of its type to survive the advent of the diesel era. 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.[1]

 Photograph of Union Pacific 4012, "Big Boy" at Steamtown, USA in Bellow Falls, Vermont
Union Pacific 4012 at Steamtown, USA in Bellow Falls, Vermont

4012 was offered to Steamtown, U.S.A along with a 4-6-6-4 Challenger and an office car. Steamtown founder F. Nelson Blount, faced with space limitations at Steamtown in 1962, could only accept the 4012. [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.[3]

The Steamtown Special History Study recommended that this locomotive remain at Steamtown because it is the only articulated locomotive in the Steamtown USA collection and recommended that due to its good condition, 4012 could be restored to working order. 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 her [could] bear her great weight".[1]


  1. ^ a b c d Chappell, Gordon. "Union Pacific No. 4012". Steam Over Scranton: Special History Study, American Steam Locomotives. National Park Service. Retrieved March 13, 2012. 
  2. ^ Boyd, Jim (2011). Steamtown In Color. Morning Sun Books. p. 37. ISBN 1582483000. 
  3. ^ "Steamtown's Locomotives and Cars". Steamtown National Historic Site. National Park Service. Retrieved March 13, 2012.