At any general election or at any special election which may be called for that purpose, the board of county supervisors of any county in this state, may or on petition of 10 per cent of the qualified electors of such county based on the total vote cast in the last county election shall, by resolution, submit to the voters of such county the proposition of creating a port district which will be coextensive with the limits of such county as now or hereafter established. Such petition shall be filed with the county clerk, who shall, within 15 days, examine the signatures thereof and certify to the sufficiency or insufficiency thereof, and for such purpose the county clerk shall have access to all registration books in the possession of the officers of any incorporated city or town in such proposed port district.