The lower of the two, at an elevation of 741 ft (226 m), carries two railroad rights-of-way (ROWs) and Altamont Pass Road, part of the old Lincoln Highway and the original alignment of US 50 before it was bypassed in 1937.

The bypass route travels over the higher summit, at 1,009 ft (308 m), and now carries Interstate 580, a major regional highway heavily congested by Central Valley suburbanization.

It carries freight trains as well as the Altamont Corridor Express, which gives its occasional name (ACE) and operates between Stockton, Livermore, Pleasanton, Fremont, and San Jose.

After 1879, when a sea level ferry crossing at the Carquinez Strait replaced the 1869 route, it remained in use for other purposes by the Southern Pacific.

After the transcontinental railroad was built through the pass by Chinese laborers in 1869, Altamont, formerly The Summit, became a critical stopping point where helper engines pushed heavy trains over the steep grades of the pass.