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Interstate 780 and path of California State Route 141

After crossing Carquinez Straight into Solano County via the Benicia-Martinez Bridge on Interstate 680 I made a western turn on I-780 towards mainline I-80.


Interstate 780 is a 7 mile freeway which runs from I-680 in Benicia westward to I-80 in Vallejo.  The corridor occupied by I-780 by a 1935 extension of Legislative Route Number 74.  Contrary to what I've read elsewhere I have never been able to find a State Highway Map from 1935 up to the 1964 State Highway indicating that LRN 74 between Vallejo east to Benicia was signed as California State Route 29.  The 1963 State Highway Map below does not display CA 29 between US 40 and CA 21 in Benicia.

1963 State Highway Map

The original routing of LRN 74 between CA 21 in Benicia west to US 40 was on Benicia Road from starting from 2nd Street.  By the 1964 Highway renumbering the freeway grade replacement of Benicia Road was completed and the route was assigned as part of I-680.

1964 State Highway Map

In 1976 the legislative definition of I-680 was changed to run north to I-80 on what was CA 21.  I-680 between Benicia and Vallejo was renumbered to I-780.

CAhighways.org on I-780

The change from I-680 to I-780 can be seen on the 1977 State Highway Map.

1977 State Highway Map

Heading westbound on I-780 the waters of Carquinez Straight are almost immediately apparent.





Access to Benicia Capitol State Historic Park can be obtained from Exit 5 for 2nd Street in Benicia.  Benicia was briefly the third California State Capitol from February 1853 to February of 1854 after San Jose and Vallejo.  The Benicia State Capitol building is the only pre-Sacramento structure still standing.


Access to Benicia State Park is signed for Exit 3A onto Columbus Parkway.



West of Exit 3A the route of I-780 enters Vallejo.


I-780 terminates at I-80.  Traffic for I-80 eastbound must take Exit 1B whereas I-80 westbound traffic must take Exit 1A.






Directly west of I-80 the path of I-780 becomes non-state maintained Curtola Parkway.  During the 1964 State Highway renumbering CA 141 was assigned to the former portion of LRN 74 between I-80 and CA 29.  At the time CA 141 appears to have used Lemon Street, Benicia Road and Maine Street to connect from I-80/I-680 to CA 29.

By 1966 the implied path of CA 141 to CA 37 appears on the State Highway Map.

1966 State Highway Map

The above proposed extension is interesting since the legislative definition extending CA 141 to CA 37 wasn't defined until 1975.

CAhighways.org on CA 141

The 1967 State Highway Map shows CA 141 on Curtola Parkway.

1967 State Highway Map

CA 141 was deleted by the legislature in 1988 according to CAhighways.org.  CA 141 appears to have never been signed in the field as ever on the 1988 State Highway Map is just shown as a legislative route. CA 141 was never completed to CA 37 but the implied path is Mare Island Way.

1988 State Highway Map

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