The original CA 26 on Bolsa Avenue and 1st Street

[Max Rockatansky]

It seems there was a barely known designation of CA 26 which once existed on LRN 183 in Orange County:

The original run of Sign State Highways were announced in the August 1934 California Highways & Public Works.  One of the initial Sign State Routes was California State Route 26 which was located in Orange County.  The original California State Route 26 followed Legislative Route Number 183 from Seal Beach to Santa Ana via Bolsa Avenue and 1st Street.  The original California State Route 26 was short lived and it would be eliminated as part of the shuffling of Sign State Route designations due to the extension of US Route 6 California.

https://www.gribblenation.org/2022/04/the-original-california-state-route-26.html