California Code, Government Code - GOV § 26002

Unless otherwise provided by law, the board may lay out, maintain, control, construct, repair, and manage public ferries, bridges, wharves, chutes, other shipping facilities, and passenger transportation facilities within the county and may cooperate with any city in so doing.

The board of supervisors may furnish and operate public transportation services within the unincorporated areas of the county. Such service may be furnished and operated within a city or transit district if the governing board of the city or district consents thereto.