California State Route 21

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Route 21

Length:

54.08 mi (87.03 km)
Numbers are before I-680 was incorporated as an interstate highway; Routing from Benicia to Cordelia: 12.45 mi (20.04 km)

Formed:

Major cities:

Fairfield
Walnut Creek
Pleasanton
Fremont

Direction:

North-South

JUNCTION	POSTMILE
See I-680 for junctions

California State Routes Unconstructed - Deleted - Scenic
< Route 20	Route 22 >

State Route 21 is a defunct north-south highway in the U.S. State of California, which Interstate 680 has wholly supplanted in the eastern part of the San Francisco Bay Area. SR 21 once ran between U.S. Highway 40 (now Interstate 80 in that location) near Cordelia and a junction with what is now State Route 238 in Fremont.

The highway ran though Solano County, California along the shore of Suisun Bay before crossing between Benicia and Martinez via a ferry--succeeded in 1962 by the Benicia-Martinez Bridge--into Contra Costa County, then passing through Concord, Pleasant Hill, Walnut Creek, and Danville before heading south into Alameda County through Dublin and Pleasanton and crossing the Hayward Hills into Fremont. Most of old SR 21's route remains as county roads or city streets, although the rapid growth of the San Francisco Bay Area has changed the surroundings of the old route significantly.

By the mid-1960s the entire route of SR 21 south of Benicia had been decommissioned after the completion of Interstate 680 north of Fremont. The remainder north of Benicia survived as the Luther Gibson Freeway to Cordelia, while Interstate 680 connected Benicia to Vallejo, California. However, in 1976 the Vallejo-Benicia segment was redesignated as Interstate 780, and the Intersate 680 designation was shifted to the Luther Gibson Freeway. Hence, the SR 21 designation was retired.