California Code, Streets and Highways Code - SHC § 111

Whenever the natural course of a State highway passes into or through any city and a State highway route through or around such city is not specifically described by law, the commission shall determine the location of the connecting portion necessary to make the State highway continuous. Such location may be either through or around such city, depending upon the commission's determination as to which location will be of the greatest benefit to through traffic upon such State highway.

Any portion of any street or highway, within the limits of such city, may be adopted by the commission as a part of the State highway system without compensation to the city.