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Interstate 680 over the Benicia-Martinez Bridge and the legacy of California State Route 21

Recently I drove Interstate 680 over Carquinez Straight via the Benicia-Martinz Bridge.  The Benicia Martinez Bridge is significant as it was location of the last major highway ferry crossing in the San Francisco Bay Area on California State Route 21.


Before the Benicia-Martinez Bridge opened in 1962 traffic on CA 21 had to take a ferry crossing over Carquinez Straight.  Traffic on CA 21 northbound entered a ferry route located on Court Street north of downtown Martinez which crossed Carquinez Straight to 5th Street in Benicia.  The alignment of CA 21 between Martinez to Benicia on the ferry route can be seen in it's final form on the 1962 State Highway Map.

1962 State Highway Map

The 1962 Benicia-Martinez Bridge is an approximately 1.7 mile long truss span design that now serves as the southbound lanes of I-680.  The 1962 Benicia-Martinez Bridge was built immediately west of 1930 Union Pacific Bridge which still is the longest rail bridge west of the Mississippi River in the United States.  The 1962 Benicia-Martinez Bridge greatly improved automotive traffic flow over Carquinez Straight and can be seen on the 1963 State Highway Map.

1963 State Highway Map

In my view it is impossible to have a legitimate historical blog/article/conversation about I-680 without including CA 21.  I-680 essentially is a modernization of the corridor occupied by CA 21.  CA 21 wasn't one of the original 1934 State Highways but was quickly added to the system by 1935.  CA 21 originally was routed from CA 17 (briefly CA 13) at Warm Springs Road northbound on the following alignment:

-  Mission Boulevard on Legislative Route Number 5 to Mission San Jose.
-  Mission Road on LRN 108 to Paloma Road. 
-  Paloma Road and Main Street in Sunol to Foothill Road.   I'm not sure if this was a spur of LRN 107 or LRN 108.
-  Foothill Road on LRN 107 to US 50 in Dublin at Dublin Boulevard.
-  Dublin Boulevard/US 50 to San Ramon Road.
-  San Ramon Boulevard on LRN 107 to Railroad Avenue in Danville.
-  Railroad Avenue to Danville Boulevard.
-  Danville Boulevard and Main Street on LRN 107 to CA 24 in Walnut Creek.
-  A multiplex of CA 24 on LRN 75 via Main Street and Contra Costa Boulevard to Pleasant Hill.  CA 24/LRN 75 split away from CA 21 in Pleasant Hill towards Concord.
-  Originally CA 21 was on County Maintained roadways between Pleasant Hill and Martinez; Contra Costa Boulevard and Pacheco Boulevard. (Note; it was likely that streets on the implied alignment of CA 21 in Martinez were likely never fully state maintained)
-  In Martinez CA 21 was aligned upon Jones Street and Pine Street to CA 4 which was originally on Escobar Street.
-  CA 21 multiplexed CA 4 on Escobar Street to Ferry Street.  CA 21 used Ferry Street to reach Court Street to the ferry over Carquinez Straight.
-  Upon crossing Carquinez Straight to 5th Street in Benicia the route of CA 21 picked up LRN 74.
-  In Benicia CA 21 followed 5th Street, L Street and 2nd Street to exit the city.
-  CA 21 used 2nd Street/LRN 74 and the general right-of-way of I-680 on Goodyear Road (I suspect the original road was razed by the Interstate) to US 40 in Cordelia.

CA 21 in it's original form can be seen on the 1938 State Highway Map.

1938 State Highway Map

By 1940 State Highways were no longer signed on non-state controlled roads.  This led to a situation where CA 21 was likely not signed between Pleasant Hill and Martinez.

1940 State Highway Map

By 1949 the legislative definition of LRN 75 had been amended to a include a spur from Pleasant Hill to Martinez.

CAhighways.org on LRN 75

State maintenance of CA 21 on Spur LRN 75 is shown between Pleasant Hill and Martinez by 1950.

1950 State Highway Map 

According to CAhighways.org the definition of Spur LRN 75 was changed in 1953 to include the Martinez-Benicia Ferry.  Apparently the City of Martinez at the time was looking at shuttering ferry service to Benicia.

By 1960 the planned route of CA 21 over the Benicia-Martinez Bridge appears on the State Highway Map.

1960 State Highway Map

By the 1964 State Highway Renumbering CA 21 was assigned as part of LRN 680.  I-680 was only signed over CA 21 from Walnut Creek over the Benicia-Martinez Bridge and the current route of I-780.

1964 State Highway Map

By 1965 I-680 appears to have been co-signed with CA 21 between Mission San Jose and Sunol.

1965 State Highway Map 

On the 1969 State Highway Map all of CA 21 south of the Benicia-Martinez Bridge is shown replaced by the completed I-680.

1969 State Highway Map

According to CAhighways.org the definition of the remaining segment CA 21 was changed in 1976 to become part of I-680 when I-780 was created.

CAhighways.org on CA 21

The modern form of I-680 and I-780 can be seen on the 1977 State Highway Map.   CA 21 is shown to be completely removed as a designation.

1977 State Highway Map

In 2007 a new span of the Benicia-Martinez Bridge was built to carry northbound I-680 traffic. The northbound span is located directly east of the 1930 Rail Bridge and is a segmental structure.  Once the 2007 Benicia-Martinez Bridge opened the 1962 Bridge was converted to southbound I-680.   In total the 1962 and 2007 structures now carry 9 lanes of I-680.

My approach to the Benicia-Martinez Bridge was from CA 4 westbound to I-680 northbound in Contra Costa County.  The CA 4/I-680 ramp is presently under going reconstruction.




From CA 4 the toll plaza for the Benicia-Martinez Bridge is signed as only 2.5 miles to the north on I-680.


Cash traffic is directed to the right hand lanes whereas Fasttrak users are directed to the left lanes.  Exit 56 for Marina Vista Avenue is the last exit before the toll booths.



Two axle vehicle tolls on the Benicia-Martinez Bridge are presently $6 dollars.



The Benicia-Martinez Bridge is presently signed as "Congressman George Miller Bridge."


The 2007 Benicia-Martinez Bridge is far from a scenic structure.  The 1930 rail bridge can be somewhat seen to the west but there isn't a single view of Carquinez Straight to be had from the actual roadway.  There is a vista point in the between the three bridges but I wasn't aware of it at the time.  My path after crossing the Benicia-Martinez Bridge had me turning west off of I-680 onto I-780.






As an interesting foot note it seems that the Martinez-Benicia Ferry and surface alignment of CA 21 north of Carquinez Straight was part of the original route of US 40/LRN 7.  The first Carquinez Bridge was completed in 1927 and it appears US 40 traffic was shifted to meet it possibly sometime between 1928 and 1930.  This can be seen by comparing the 1928 State Highway Map to the 1930 edition.

1928 State Highway Map 

1930 State Highway Map

It should also be noted that the Lincoln Highway moved from Altamont Pass and followed US 40 over the Carquinez Bridge when it opened in 1927. 

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