Idaho Code § 70-1102
At any election which may be called for that purpose, subject to the provisions of section 34-106, Idaho Code, the board of county commissioners of any county in this state which qualified under section 70-1101, Idaho Code, may, or in petition of ten per cent (10%) of the qualified electors of such county, based on the total vote cast in the county in the last general election, shall by resolution, submit to the voters of such county the proposition of creating a port district with boundaries co-extensive with the boundaries of such county. Such county commissioners may also submit to such vote the proposition of creating a port district with boundaries less than county-wide upon their own resolution, or shall submit the same upon petition as provided in section 70-1103, Idaho Code. No port district shall, at the time of its formation, include lands in more than one (1) county.
Idaho Code § 70-1102