Mo. Rev. Stat. § 247.240
Metropolitan water supply districts may be of any size and may include all or any part of any county, or of two or more adjoining school districts, cities, towns, villages or public water supply districts or other political subdivisions within a county; no two metropolitan water supply districts shall overlap; no more than one metropolitan water supply district may be formed in any one county; provided however, that no city, town, village or public water supply district having a water supply or distribution system shall be included in a metropolitan water supply district, until said municipality shall consent to become included as evidenced by an ordinance or resolution passed by a majority vote of the governing body of such municipality; and provided further, that the territory within any metropolitan water supply district organized under sections 247.230 to 247.670 should be contiguous.
§ 247.240, RSMo