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Union Pacific Big Boy Nr. 4018

Big Boy was the name given to the Union Pacific Railroad's twenty-five 4000 class 4-8-8-4 Mallet articulated steam locomotives built between 1941 and 1944 by Alco. The longest ever build in the world.



It's 1 of 8 remaining in the USA.



http://en.wikipedia.org/wiki/Union_Pacific_Big_Boy