One of the busiest freeways in the East Bay, Interstate 680 connects the communities of Benicia, Concord, Walnut Creek, Danville, Sunol and San Jose. The section between Interstate 580 and the Benicia Bridge underwent extensive reconstruction through the late 1990s, resulting in an eight to ten lane freeway with carpool lanes.
Additionally Interstate 680 through the Sunol Grade was improved in 2001-2003. As part of the eight lane expansion, two bridges that were constructed in part for the planned interchange with SR 238 (Hayward Bypass/Mission Freeway) were removed.
Prior to the completion of I-280 and I-680 to their shared end point at U.S. 101, Temporary routes were posted along SR 17 through San Jose – 1968 California Official Map
The Interstate 680 corridor was previously part of California State Route 21. Construction of the freeway gradually overtook the state route between San Jose and Fairfield in the 1960s and 1970s.
Prior to 1976, the northern most extent of Interstate 680 turned west from Benicia to I-80 at Vallejo. This changed with both the establishment of Interstate 780 along the former western leg to Vallejo and the extension of I-680 north over what was the remaining section of SR 21 between Benicia and I-80 at Coredlia.
The 1.2 mile long, Benicia-Martinez deck-truss Bridge over the Sacramento-San Joaquin River Delta was augmented with a parallel bridge. Started in 2001, this project involved the replacement of approaches for northbound traffic along with a new bridge structure located east of the original span. Following completion of the second span on August 25, 2007, the existing 1962 bridge was retrofitted to meet state seismic standards and restriped to carry southbound traffic. With the completion of the $1.2 billion project, the regular congestion that occurred as part of the reduced lanes, toll plazas, and the adjacent interchange with I-780 diminished.1