California Code, Public Resources Code - PRC § 5023

(a) It shall be the duty of the Department of Transportation to keep in repair all objects or markers adjacent to a state highway which have been erected to mark registered historical places and to keep such monuments or markers free from vegetation which may obscure them from view.

(b) It shall be the duty of the county authorities, in charge of county highways, and all city authorities, with respect to streets and highways under their respective jurisdictions, to keep in repair or cause to be kept in repair all objects or markers adjacent to a public highway which have been erected to mark registered historical places and to keep such markers and monuments free from all vegetation which may obscure them from view.

(c) It shall be the duty of the department to keep in repair or cause to be kept in repair all objects, markers and monuments designating any registered historical places in respect to which no obligation in respect thereto is imposed on other governmental agencies by this section, and the department shall keep such markers and monuments free from all vegetation which may obscure them from view.