Summit Tunnel

After almost five years of sustained construction effort, in the late Spring of 1868 the Central Pacific Railroad finally 'conquered' the Sierra Nevada Mountains with the successful completion at Donner Pass of its 1,659-foot Tunnel #6 (aka 'The Summit Tunnel') thus permitting the mass transportation of passengers and freight over the Sierra range for the first time.

The Summit Tunnel was used continuously for 130 years by the trains of the Central Pacific, Southern Pacific, Union Pacific, and AMTRAK. It is now bypassed and sits idle.

(via Information Junk)