The board of supervisors of any county by itself or by joining with the board of supervisors of any county adjacent to such county may form a zoological park and garden district. The board of supervisors of any county or counties wishing to form such a district may do so by entering into a contract for the construction, expansion, remodeling and/or maintenance and equipping of such zoological park and garden. Such contract or any future contract may provide for the continued use, equipping, repairing, reconstructing and remodeling of such park and garden.