Cal. Sts. & High. Code § 27324

After all protests have been disposed of in the same manner as protests upon the incorporation of the district, the Secretary of State shall issue his certificate certifying to the annexation and describing the boundaries of the district as finally determined, which certificate shall be recorded in the office of the county recorder of each county wherein any portion of the annexed territory is located, and thereupon the boards of supervisors of the county shall appoint a member or members of the board to serve until the expiration of the term of the directors then holding for the term of office that will soonest expire.