&sq=Envato&lang=en&file=File:I-680_(CA).svg) Interstate 680 | ||||
|---|---|---|---|---|
 I-680 highlighted in red | ||||
| Route information | ||||
| Auxiliary route of I-80 | ||||
| Maintained by Caltrans | ||||
| Length | 70.52 mi[1] (113.49 km) | |||
| History | State highway in 1933; Interstate in 1955 | |||
| Tourist routes |  I-680 between Mission Boulevard (SR 238) in Fremont to SR 24 in Walnut Creek[2] | |||
| NHS | Entire route | |||
| Major junctions | ||||
| South end |   I-280 / US 101 in San Jose | |||
| North end |   I-80 / SR 12 in Fairfield | |||
| Location | ||||
| Country | United States | |||
| State | California | |||
| Counties | Santa Clara, Alameda, Contra Costa, Solano | |||
| Highway system | ||||
| ||||
Interstate 680 (I-680) is a north–south auxiliary Interstate Highway in Northern California. It curves around the eastern cities of the San Francisco Bay Area from San Jose to I-80 at Fairfield, bypassing cities along the eastern shore of San Francisco Bay such as Oakland and Richmond while serving others more inland such as Pleasanton and Concord.
Built in the 1920s as SR 21 and designated in 1955, I-680 begins at a junction with I-280 and US Route 101 (US 101/Bayshore Freeway) and heads northeast and north-northwest through the northeast part of San Jose. After passing State Route 237 (SR 237) in Milpitas and SR 262 in Fremont, I-680 abruptly turns northeast (where a connection to a SR 238 freeway was planned) and enters the hills and valleys of the California Coast Ranges. The highway crosses over Mission Pass, also known as the Sunol Grade, and descends into the Sunol Valley, where it meets SR 84 near Sunol. From Sunol, I-680 again heads north-northwesterly through valleys, including the San Ramon Valley, along the Calaveras Fault. Junctions along this portion include I-580 in Dublin and SR 24 in Walnut Creek. Beyond the latter interchange, a three-way directional junction with the SR 24 freeway west to Oakland, I-680 heads north into Pleasant Hill, where SR 242 splits and I-680 again heads northwesterly. After the junction with SR 4 in Martinez, the highway crosses the Carquinez Strait on the Benicia–Martinez Bridge, immediately meeting the east end of I-780 on the Benicia end. The remainder of I-680, from Benicia to I-80 at Fairfield, lies between a hilly area to the west representing the southwestern tip of the Vaca Mountains, and a marshy area (along the Suisun Bay and Cordelia Slough) to the east.[3]
- ^ "Table 2: Auxiliary Routes of the Dwight D. Eisenhower National System Of Interstate and Defense Highways". FHWA Route Log and Finder List. Federal Highway Administration. December 31, 2021. Retrieved July 12, 2022.
- ^ California Department of Transportation (August 2019). "Officially Designated State Scenic Highways and Historic Parkways" (XLSX). Sacramento: California Department of Transportation.
- ^ Google Maps street maps and USGS topographic maps, accessed February 2008 via ACME Mapper