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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 at Oakland in Alameda County.  CA 24 is one of the original signed state highways but might be the most truncated as it originally ended at what is now US 395 near the Nevada State Line.  CA 24 is primarily a commuter route for traffic heading into the Bay Area and traverses 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 is CA 13 on Tunnel Road.

 
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.  LRN 75 which carried CA 24 from Walnut Creek to the Caledcott Tunnels is shown as running unsigned on Broadway west to US 50.  The original alignment of CA 24 along with the LRN 206 and LRN 75 can be observed on the 1963 State Highway Map City insert for Oakland.

1963 State Highway Map City Insert

By 1964 CA 24 was shown still traversing Tunnel Road and Ashby but the LRN had been switched from 206 to 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

I-980 was created in 1976 which cut back CA 24 to I-580 where it currently terminates.



Tracking down the rest of the original alignments of CA 24 is tricky given the previous size of the route. Fortunately CAhighways.org already has all the previous alignment and truncation history for CA 24 available.

CAhighways.org on CA 24

Really CA 24 I think is the poster child for why the State Highways were renumbered.  Not only was 24 on multiple LRNs but the alignment in general shifted directions multiple times and had numerous multiplexes that really weren't necessary. As much as I don't care for much of the renumbering conventions piecing up CA 24 into multiple state highways was a solid concept in my opinion.

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