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November Bay Trip Part 3; California State Route 24

After leaving Mount Diablo State Park I drove through Walnut Creek to reach California State Route 24 to continue heading westward into Oakland.


CA 24 is a 13.5 mile east/west freeway between I-680 at Walnut Creek in Contra Costa County to I-580/I-980 at Oakland in Alameda County.  CA 24 is one of the original 1934 signed state highways but also is the most truncated which still exists.  CA 24 in it's full 1935 scope began at US 40 in Berkeley and crossed the Sierra Nevada Range to what is now US 395 near the Nevada State Line.  What was one of the grandest State Highways in California is now primarily a commuter route for traffic heading into the Bay Area through the Diablo Range.




CA 24 traverses through the Caldecott Tunnel which has four two-lane bores.  The first two bores carry the eastbound freeway and were completed back in 1937.  The third bore which is now the southern westbound lanes opened in 1964 with the final bore I traveled through in the picture below opened in 2013.


The only major highway junction on CA 24 between I-680 and I-580/I-980 is CA 13 on Tunnel Road.


CA 24 terminates at I-580/I-980 in Oakland.  The CA 24 freeway originally extended into downtown Oakland west of I-580.  By 1976 this segment was designated as future I-980 which was transferred to the new designation by 1981.  I-980 was completed between I-580 and I-880 by 1986.



Prior to 1970 CA 24 took the current alignment of CA 13 north of the Caldecott Tunnels westward to US 40 via Tunnel Road and Ashby Avenue.  The segment of modern CA 13 was part of Legislative Route 206 which designated by the State Legislature in 1935 according to CAhighways.org.  Apparently when CA 24 was designated in 1934 terminated in Sacramento but was extended to US 40 on San Pablo Avenue in Berkeley via LRN 11 and LRN 75 in 1935.

CAhighways.org on LRN 206

CAhighways.org on CA 24

LRN 75 in 1935 carried CA 24 from CA 21 at Main Street in Walnut Creek westward on Mount Diablo Boulevard to LRN 206 via Old Tunnel Road and it's 1903 era tunnel to Tunnel Road.  As stated above the first two bores of Caldecott Tunnel were completed by 1937 which eliminated the large mountain grade that separated the Oakland area from Walnut Creek.  LRN 75 continued unsigned on Broadway west to US 50.  CA 24, LRN 206 and LRN 75 can be seen on their original configurations through the Oakland area on the 1938 State Highway Map City Insert.

1938 State Highway Map City Insert

It appears most of CA 24 from Walnut Creek west to the Caldecott Tunnel was upgraded to expressway/freeway standards during the 1960s.  This expansion appears to align with the third bore of the Caldecott Tunnel in 1963.

1963 State Highway Map City Insert

Regarding LRN 75 it is mostly associated with CA 4.  LRN 75 was designated between Oakland and Walnut Creek in 1931.  LRN 75 was extended to Altaville near Angel's Camp in 1933 according to CAhighways.org.

CAhighways.org on LRN 75

By 1964 CA 24 was shown still traversing Tunnel Road and Ashby but the LRN had been switched from 206 to 13 in anticipation of it being signed as CA 13.  LRN 75 west of the Caldecott Tunnels on Broadway was changed to LRN 24, I-80 can be seen gradually replacing US 40 as well.  The implied routing of LRN 24 south of US 50 to CA 17 (now I-880) is shown along the modern I-980.  I-580 also makes and appearance multiplexed with US 50.

1964 State Highway Map City Insert

By 1965 the implied routing of CA 24 west of the Caldecott Tunnels to US 50  appears on the city insert for Oakland. 

1965 State Highway Map City Insert

By 1967 I-80 had replaced US 40 at the western terminus of CA 24's surface alignment.

1967 State Highway Map City Insert

The CA 24 freeway west of the Caldecott Tunnels is shown complete by 1970.

1970 State Highway Map City Insert

As stated in the intro the route of CA 24 in it's maximum scope was one of the grandest State Highways in terms of length and importance.  It's somewhat ironic that CA 24 still exists albeit on a small section that wasn't part of the original 1934 designation.  The following post 1964 State Highways follow the general right-of-way of CA 24:

-  CA 13 from I-880 to CA 24
-  I-680 to CA 242
-  CA 242 to CA 4
-  CA 4 to CA 160
-  CA 160 to Sacramento where it would have followed CA 16 out of the city.
-  CA 16 to CA 113
-  CA 113 to US 99E
-  US 99E to CA 20
-  CA 20 to CA 70
-  CA 70 to CA 7/US 395

Of note CA 24 before the 1964 renumbering was straightened north out of Sacramento via what is now CA 99 and CA 70 to Marysville.  US 40A had also been designated over what was CA 24 on the modern alignments of CA 113 and CA 70.  CA 24 has been a frequent topic in many of my blogs which cover former portions of the highway:

California State Route 13

-  This blog covers mostly the Warren Freeway but goes into greater detail regarding former CA 24 on Ashby Avenue and Tunnel Road.

California State Route 242

-  This blog covers what was CA 24 east of Walnut Creek through Concord.  Oddly CA 242 was signed as part of CA 24 at least until 1988 according to my map research.  A wide bypass of Concord which CA 24 was to be built upon was planned but never has fallen off State Highway Maps. 

Disaster Tourism Road Trip Part 8; CA 160 and CR J11 in the Sacramento River Delta

-  This blog covers much of what was CA 24 in the Sacramento River Delta on current CA 160. 

Highways in and around Old Sacramento; US 40, US 99W, CA 16, CA 24, CA 70, CA 99, CA 275 and more

-  This blog covers the history of surface highways in Sacramento which includes CA 24.  CA 24 went through massive realignments in Sacramento before the 1964 State Highway renumbering.

CA 113; a little big of vintage US 40, US 40A, US 99W and CA 24

-  This blog covers the route of CA 113 which assumed portions of what were CA 24 between Woodland and Tudor. 

California State Route 70; the Feather River Highway

-  CA 70 is the largest segment of CA 24 to be split off and was even part of US 40A at one point.  In my personal opinion CA 70 as a standalone highway is one of the greatest transportation marvels in the State Highway system.

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