In California, it follows the original corridor of the Lincoln Highway from Sacramento to Reno (with minor deviations near Donner Summit).

[9] According to the California Streets and Highways Code, most maps, and local signs, I-80 begins at the interchange with US 101 in San Francisco.

[10][11] The federal and state governments disagree as to whether this westernmost segment of the signed Interstate, known as the San Francisco Skyway or Bayshore Viaduct, is actually part of the Interstate Highway System,[10][11] although it is consistently shown as I-80 on most maps of San Francisco.

This segment suffers from severe traffic congestion during rush hour due to the merger of three freeways (I-80, I-580, and I-880) at the MacArthur Maze.

[14] The Eastshore Highway began in El Cerrito at an intersection with San Pablo Avenue at Hill Street between Potrero Avenue and Cutting Boulevard,[15] adjacent to the location today of the El Cerrito del Norte station of Bay Area Rapid Transit (BART).

The Eastshore Highway ran from El Cerrito to the San Francisco–Oakland Bay Bridge along the same routing as today's freeway, although it was much narrower.

In the stretch from University to Ashby avenues in Berkeley, this resulted in the creation of an artificial lagoon which was developed by the Works Progress Administration (WPA) in the late 1930s as Aquatic Park.

Checkpoints are often set up to enforce chain restrictions on vehicles bound for icy or snowy areas.

The pass is generally open year-round; it is plowed in winter but may temporarily close during the worst snowstorms.

The older, original US 40/Lincoln Highway route over Donner Pass is about two miles (3.2 km) to the south.

US 40 was one of the original California routes designed in 1926, although its west end was in Oakland with US 101E (then SR 17, then I-5W, now I-580/I-880) prior to the San Francisco–Oakland Bay Bridge opening in 1936.

US 40 and US 50 both followed the San Francisco–Oakland Bay Bridge and the routes split on what is the present day MacArthur Maze in Oakland.

At one point, it travels right by Donner Lake, unlike I-80, which ascends higher in the Sierra Nevada north of historic US 40.

The Panhandle Freeway was to be routed through Hayes Valley, passing through Golden Gate Park and terminating at proposed I-280, now SR 1.

A January 1968 amendment moved I-280 to its present alignment, degraded I-480 to a state highway, and truncated the origin point of I-80 to the Embarcadero Freeway (then I-280, formerly I-480).

Along Oak and Fell, the planners suggested an underground road running more than 0.5 miles (0.80 km) from Laguna to Divisadero streets.

However, the roads would violate the long-standing general plan for San Francisco, which calls for no new highway capacity.

[34] Driving across the Sierra Nevada became far easier with the construction of I-80 across Donner Summit since that pass is closed only for intense snowstorms.

[citation needed] In 1964, Caltrans desired to reduce the number of designated routes in the California state highways system.

The now-designated Capital City Freeway was then the original I-80 routing, continuing southwest directly into downtown Sacramento.

I-880 would have intersected SR 244 and then US 50, but, in 1979, the Sacramento City Council voted to delete the proposed I-80 alignment for rail transit.

SR 244 was then truncated from its proposed alignment to the only freeway section of the abandoned project in 1994, which is about a mile (1.6 km) long.

[41] In 2002, due to the risk of a future large earthquake, Caltrans started building a new eastern span.

The project includes converting the existing 8-mile (13 km) carpool lanes between Red Top Road and Air Base Parkway.

[44] In May 2024, the California Transportation Commission approved $105 million for a project that would add HOT lanes between Davis and West Sacramento.