This is the only place in the world to see both the largest steam engine and the largest diesel locomotive ever to ride the rails. The Union Pacific’s 594-ton “Big Boy” 4014 steam-powered engine shares the spotlight with the Union Pacific Centennial DD40X diesel-powered locomotive, which measures nearly 100 feet in length.
Diesel
http://en.wikipedia.org/wiki/EMD_DDA40X
Big Boy
http://en.wikipedia.org/wiki/Union_Pacific_Big_Boy
http://www.youtube.com/watch?v=TWpPeugUI44
http://en.wikipedia.org/wiki/Union_Pacific_4014