Cal. Gov. Code § 26490

The board of supervisors may designate an existing county historical commission or county museum commission to foster and promote the preservation of historical records. An existing commission to be so designated may include in its membership the county clerk or his designate, the county librarian or his designate, and the county museum director (if one exists) or his designate. If no such commission has been designated, the board of supervisors may appoint a historical records commission to foster and promote the preservation of historical records. The commission shall be composed of the county clerk or his designate, the county librarian or his designate, the county museum director (if one exists) or his designate, and two or three additional members for a total of five members.