Interstate 680 (California)

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
Major intersections	SR 130 in San Jose SR 237 in Milpitas SR 262 in Fremont SR 238 in Fremont SR 84 near Sunol I-580 on the Dublin / Pleasanton border SR 24 in Walnut Creek SR 242 near Concord SR 4 in Martinez I-780 in Benicia
North end	I-80 / SR 12 in Fairfield
Location
Country	United States
State	California
Counties	Santa Clara, Alameda, Contra Costa, Solano
Highway system
Interstate Highway System Main Auxiliary Suffixed Business Future State highways in California Interstate US State Scenic History Pre‑1964 Unconstructed Deleted Freeways
← I-605 → I-710

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]