Interstate 680 (California)

Interstate 680 (California)

Interstate 680 (I-680) is a north–south Interstate Highway in northern California. It curves around the eastern cities of the San Francisco Bay Area from San Jose to Interstate 80 at Cordelia, 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 and designated in 1955, I-680 begins at a junction with I-280 and US 101 (Bayshore Freeway), and heads northeast and north-northwest through the northeast part of San Jose. After passing 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 a hilly area. 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 Cordelia, lies between a hilly area to the west and a marshy area (along the Suisun Bay and Cordelia Slough) to the east.

I-680 is part of the State Scenic Highway System from SR 238 in Fremont north to SR 24 in Walnut Creek, and is eligible for said system from SR 238 south to the Alameda-Santa Clara County line.