Altamont Pass is a 1,009 ft (308 m) mountain pass in the Diablo Range between Livermore in the Livermore Valley and Tracy in the San Joaquin Valley in Northern California.
The pass carries Interstate 580, heavily congested by Central Valley suburbanization, Altamont Pass Road, which is the original alignment of US 50 before it was bypassed by the present I-580, and two railroad right-of-ways (ROWs).
Only one right-of-way is still in use: the old Western Pacific line, now owned by Union Pacific; it is today used for the Altamont Commuter Express, with service to Livermore, Pleasanton, Fremont, and San Jose. The abandoned right-of-way was used by Southern Pacific, which is now part of Union Pacific. This line was the Bay Area's original connection to the transcontinental railroad and was abandoned in 1984 in favor of trackage rights on the ex-Western Pacific line.
The Altamont Pass area was home to the Altamont Speedway from 1966 to 2008, which was known for being the site of the 1969 Altamont Free Concert, a large concert marred by violence. The pass is also known for the Altamont Pass Wind Farm, one of the earliest in the United States.
