When any incorporated city or town shall have decided to establish and maintain public parks under sections 90.500 to 90.570, the mayor of such city shall, with the approval of the legislative branch of the municipal government, proceed to appoint a board of nine directors for the same, chosen from the citizens at large with reference to their fitness for such office, and no member of the municipal government shall be a member of the board.
§ 90.520, RSMo