Altamont Pass, Rail mountain pass in Diablo Range, California.

Altamont Pass is a mountain crossing in the Diablo Range that connects two valleys in Northern California using two different elevation levels. The lower railway corridor sits at about 230 meters (755 feet) elevation, while Interstate 580 runs through the higher passage at about 310 meters (1,020 feet).

The pass was called Livermore's Pass after Robert Livermore, owner of Rancho Las Positas and a way station, from the Gold Rush era. Chinese laborers built the transcontinental railroad through it in 1869, with a 1,200-foot summit tunnel. The settlement at the summit, first called The Summit, later took the name Altamont; its post office closed in 1955.

The pass takes its name from Alta Monte, the Spanish-style name adopted by the summit settlement founded when the railroad arrived in 1869; the post office there closed in 1955. The Altamont Corridor Express commuter service, named after the pass, runs between Stockton, Livermore, Pleasanton, Fremont and San Jose. The Altamont Speedway east of the pass hosted the 1969 Altamont Free Concert with The Rolling Stones, marred by violence.

The passage sees daily use by Union Pacific freight trains and commuter trains that run multiple times daily between the valleys. Visitors should know that access to the railway corridors is restricted, but the area is visible from the highway.

Hundreds of wind turbines from the Altamont Pass Wind Farm harness the strong winds flowing through this natural passage to generate electricity. These wind farms shape the landscape and make the pass an important renewable energy location in the region.