California State Route 24
|Defined by S&HC § 324|
|Maintained by Caltrans|
|Length:||13.492 mi (21.713 km)|
|Existed:||1934 – present|
|West end:||I-580 / I-980 in Oakland|
|East end:||I-680 / Mount Diablo Boulevard in Walnut Creek|
State Route 24 (SR 24) in the U.S. state of California is a heavily traveled east–west freeway in the eastern side of the San Francisco Bay Area of northern California that runs from the Interstate 580/Interstate 980 interchange in Oakland, and through the Caldecott Tunnel under the Berkeley Hills, to the Interstate 680 junction in Walnut Creek. It lies in Alameda County, where it is highly urban, and Contra Costa County, where it passes through wooded hillsides and suburbs.
This route is part of the California Freeway and Expressway System and is eligible for the State Scenic Highway System. Caltrans has only designated it as a scenic highway between the eastern end of the Caldecott Tunnel and I-680, however. SR 24 is designated as both the Grove Shafter Freeway (named after streets the route travels along - Grove Street was later renamed Martin Luther King Jr. Way) and the William Byron Rumford Freeway from the Caldecott Tunnel to the I-580 interchange segment of the MacArthur Maze, continuing henceforth as I-980 to the terminus with I-880.
SR 24 begins at the four-level interchange with Interstate 580 and Interstate 980 in Oakland; this interchange is located on top of Grove Shafter Park. SR 24 initially heads north before turning east near the Berkeley city limits. Route 24 rises from near sea level in downtown Oakland past its interchange with State Route 13, which is a freeway south of SR 24 (completed August 1999) and a surface street north of SR 24. After this, SR 24 crosses the Contra Costa County county line through the four-bore Caldecott Tunnel and offers some attractive views of the hilly terrain through which it passes. Some protection of the views comes from the highway's designation as a California Scenic Highway. 
On the other side of the tunnel, SR 24 travels through unincorporated Contra Costa County before entering Orinda. SR 24 crosses the Mokelumne Aqueduct soon after entering the city of Lafayette. SR 24 terminates at the intersection with Interstate 680 just inside the city limits of Walnut Creek.
Highway 24 was designated in 1932 in conjunction with the ongoing construction of the Broadway Low Level Tunnel (subsequently renamed the Caldecott Tunnel) which opened in 1937, connecting with the new Eastshore Highway and the approaches to the new Bay Bridge by way of Ashby Avenue through Berkeley west of the Berkeley Hills, and routed along Mount Diablo Boulevard through Contra Costa County east of the hills.
Highway 24 remained along Ashby Avenue until completion of the Grove-Shafter Freeway in the late 1960s. This new freeway, which ran from the Caldecott Tunnel through downtown Oakland to the MacArthur and Nimitz Freeways, was designated Route 24 and Ashby was re-designated Route 13.
Route 24 used to extend much further east. The section of Interstate 680 between the current terminus of SR 24 and State Route 242 was dual-signed I-680 and SR 24 until ca. 1987; State Route 242 which runs primarily in Concord was signed as Route 24 until the same time. Older maps show routes for 24 which continue along State Route 4 from the current intersection of 242 to the Antioch Bridge, continuing along the river road to Sacramento, currently State Route 160, then continuing north to Woodland, Marysville, Oroville, along the North Fork of the Feather River to a junction with State Route 89, where it continued dual-numbered with 89 through Quincy. Highway 24 split from 89 near Graeagle, and continued east through Portola east until its terminus at U.S. Route 395. Parts of the same route were also sometimes designated as State Route 84.
Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, and do not necessarily reflect current mileage. R reflects a realignment in the route since then. The numbers reset at county lines; the start and end postmiles in each county are given in the county column.
|Oakland||R1.85||I-980 to I-880 – Downtown Oakland||Continuation beyond I-580|
|R1.85||2A||I-580 (MacArthur Freeway) – San Francisco, Hayward||Westbound exit and eastbound entrance|
|2B||Martin Luther King Jr Way, 51st Street||Eastbound exit and westbound entrance|
|R3.06||3||Telegraph Avenue||Westbound exit and eastbound entrance|
|R3.32||3||Claremont Avenue||Eastbound exit and westbound entrance|
|R3.55||4A||College Avenue||Westbound exit only|
|R4.15||4B||Broadway||Signed as exit 4 eastbound|
|R5.12||5A||SR 13 south (Warren Freeway) – Hayward||Signed as exit 5 eastbound|
|R5.12||5B||SR 13 north (Tunnel Road) – Berkeley||Eastbound exit is via exit 4|
|R5.47||6||Tunnel Road||Signed as "Old Tunnel Road" eastbound|
|Oakland||Caldecott Tunnel under Berkeley Hills|
|R0.40||7A||Fish Ranch Road|
|Orinda||1.20||7B||Wilder Road||Formerly Gateway Boulevard, renamed February 2010|
|R2.32||9||Orinda, Moraga (Camino Pablo)|
|R3.47||10||St. Stephens Drive, Hidden Valley Road|
|Lafayette||R4.40||11||Acalanes Road, Mount Diablo Boulevard, Upper Happy Valley Road|
|R6.51||12||Oak Hill Road – Central Lafayette, Moraga||Signed as exit 13 westbound|
|R7.66||14||Pleasant Hill Road, Mount Diablo Boulevard|
|Walnut Creek||R9.12||15||I-680 / Ygnacio Valley Road – Sacramento, Concord, San Jose, Dublin||Eastbound exit and westbound entrance; signed as exits 15A (south) and 15B (north)|
|R9.12||15A||Mount Diablo Boulevard||Eastbound exit and westbound entrance|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi
- California Highways: State Route 24
- Staff. "State Truck Route List" (XLS file). California Department of Transportation. Retrieved August 21, 2012.
- CA Codes (shc:250-257)
- CA Codes (shc:260-284)
- "Officially Designated State Scenic Highways and Historic Parkways". California Department of Transportation. December 7, 2007. Retrieved June 22, 2011.
- 2007 Named Freeways, Highways, Structures and Other Appurtenances in California. Caltrans. p. 126. Retrieved 2007-03-28.
- Thomas Brothers (2000). California Road Atlas and Driver's Guide (Map). p. L,158,156.
- Rand McNally (2008). The Road Atlas (Map). p. 13.
- CalTrans State Highway Routes Selected Information 1995, p.39
- National Automobile Club. Road Map of North Central California (Map) (undated, before 1956 ed.). Section Section 2.
- California Department of Transportation, Log of Bridges on State Highways, July 2007
- California Department of Transportation, All Traffic Volumes on CSHS, 2005 and 2006
- California Department of Transportation, California Numbered Exit Uniform System, State Route 24 Freeway Interchanges, Retrieved on 2009-02-05.
|Wikimedia Commons has media related to California State Route 24.|
- California @ AARoads - State Route 24
- Caltrans: Route 24 highway conditions
- California Highways: SR 24
- Alternate routes considered for Route 24 in Oakland