California State Route 23
|Defined by Streets and Highways Code § 323|
|Maintained by Caltrans|
|Length:||32.030 mi (51.547 km)
SR 23 is broken into pieces, and the length does not reflect the US 101 and SR 118 overlaps that would be required to make the route continuous.
|South end:||SR 1 in Malibu|
| US 101 in Thousand Oaks
SR 118 in Moorpark
|North end:||SR 126/A St in Fillmore|
Route 23 is known as the Military Intelligence Service Memorial Highway from US 101 to California Route 118, in honor of the U.S. 100th Infantry Battalion and 442nd Regimental Combat Team, composed entirely of Japanese Americans.
Route 23 consists of three distinct sections. The southern section begins as Decker Canyon Road near Trancas in Malibu, where Route 23 intersects with the Pacific Coast Highway (State Route 1), or "PCH." This portion provides numerous beautiful vistas of the Santa Monica Mountains and the Pacific Ocean during daytime, but extreme caution is advisable, especially as the road nears PCH. It is a notoriously dangerous road, and the rusted chassis of cars that have gone over the side can still be seen. Philip Taylor Kramer, bassist with the rock band Iron Butterfly from 1974-1977, allegedly committed suicide by driving his van over the side along this route. Along its steep and winding path through the Santa Monica Mountains as an increasingly tight and twisting canyon road until its intersection with Potrero Road, Route 23 becomes Westlake Boulevard, where it departs Los Angeles County for Ventura County and heads roughly two miles northeast through the Westlake section of Thousand Oaks, a developed residential community. SR 23 then merges with Ventura Freeway (U.S. Route 101) and runs concurrently with it north to the Moorpark Freeway.
The middle section, known as the Moorpark Freeway, is a major route for traffic headed between Thousand Oaks and Moorpark. It starts in Thousand Oaks, splitting off from the concurrency with Route 101 and heading north, with three lanes in both directions. The Moorpark Freeway terminates at the exit for Los Angeles Avenue when the freeway turns east to become the Ronald Reagan Freeway (State Route 118). Funding for widening of the freeway was approved August 18, 2005, with construction to begin in February 2006, to be completed in 2009. The widening was completed ahead of schedule in April 2008. Traffic along this freeway during rush hour is extremely congested, particularly near the intersection with the 101.
The northernmost section begins at State Route 118 in Moorpark (called Los Angeles Avenue in Moorpark), and heads north as Grimes Canyon Road through orange groves and sandstone cliffs. In Fillmore, it terminates at State Route 126. The road in Fillmore actually continues past Route 126 up to the foot of the Los Padres National Forest.
On SR 23 from Tierra Rejada Road and Olsen Road (and vice versa) is a bike lane. After crossing Tierra Rejada Road (going north) and Olsen Road (going south), bicyclists are prohibited from crossing.
State Route 23 has been designated as such since 1934. However, at this time it was also designated as Legislative Route 155. The freeway portion of SR 23 opened in several phases between 1971 and 1994. Before then, SR 23 intersected with U.S. 101 near Newbury Park, although it still ran concurrently with U.S. 101, which was then an expressway.
SR 23 was designated as part of the Freeway and Expressway System in 1959.
Decker Freeway was a never built north–south freeway that would connect CA 118, US 101, and CA 1. The freeway was part of a 1958 plan by the Metropolitan Engineering Board, but was later considered to be geographically improbable and the plans were abandoned.
The freeway's southern portion, from CA 1 to US 101, follows the general alignment of Decker Canyon Road and Westlake Blvd, a segment of CA 23. It would continue north before terminating at CA 118 near First Street.
Except where prefixed with a letter, postmiles were measured on the road as it was in 1964, based on the alignment that existed at the time, and do not necessarily reflect current mileage. R reflects a realignment in the route since then, M indicates a second realignment, L refers an overlap due to a correction or change, and T indicates postmiles classified as temporary (for a full list of prefixes, see the list of postmile definitions). Segments that remain unconstructed or have been relinquished to local control may be omitted. The numbers reset at county lines; the start and end postmiles in each county are given in the county column.
|Malibu||0.00||SR 1 (Pacific Coast Highway) – Oxnard, Santa Monica||South end of SR 23|
|US 101 south (Ventura Freeway) / Westlake Boulevard – Los Angeles||Interchange; south end of US 101 overlap; US 101 exit 40|
|South end of freeway on US 101|
|1.62[N 1]||41||Hampshire Road|
|12B||US 101 north (Ventura Freeway) – Ventura||North end of US 101 overlap; no exit number northbound; US 101 north exit 43A, south exit 43B|
|R3.70||13||Hillcrest Drive, Thousand Oaks Boulevard – Thousand Oaks||Southbound exit and northbound entrance|
|R6.03||15||Avenida de los Arboles|
|R7.17||16||Sunset Hills Boulevard|
|R8.21||17||Olsen Road – Simi Valley|
|Moorpark||R10.16||19||Tierra Rejada Road|
|North end of freeway|
|20B||SR 118 east (Ronald Reagan Freeway) – Los Angeles||Interchange; south end of SR 118 overlap; no exit number southbound; SR 118 south exits 18A-B|
|SR 118 west (Los Angeles Avenue) / Moorpark Avenue – Saticoy, Ventura||North end of SR 118 overlap|
|Fillmore||24.17||SR 126 (Ventura Street) – Santa Clarita, Santa Paula, Ventura||North end of SR 23|
|24.17||A Street||Continuation beyond SR 126|
|1.000 mi = 1.609 km; 1.000 km = 0.621 mi
- California Department of Transportation. "State Truck Route List". Sacramento: California Department of Transportation. Archived from the original (XLS file) on June 30, 2015. Retrieved June 30, 2015.
- CA Codes (shc:250-257)
- 2007 Named Freeways, Highways, Structures and Other Appurtenances in California (PDF). Caltrans. p. 126. Retrieved 2007-03-28.
- California Highways
- Shell California (Map). Cartography by The H.M. Gousha Company. Shell Oil Company. 1965. § R3.
- 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 23 Freeway Interchanges, U.S. Route 101 Freeway Interchanges, Retrieved on 2009-02-05.