Mo. Rev. Stat. § 64.070
After the county commission shall have adopted such subdivision regulations, no plat of a subdivision of land within the unincorporated area of such county shall be recorded until such plat shall first have been submitted to the planning commission. If the county planning commission does not report upon the plat within thirty days, it may then be deemed approved. If such plat be amended or rejected by the planning commission, such action may be overruled and the plat approved only by the county commission, provided the reasons for such overruling shall be spread upon the minutes of said county commission. The recorder of deeds shall not record a plat of a subdivision of land in the unincorporated area of the county until he shall have received a certificate of authority from the county zoning enforcement officer, who shall issue such certificate if such plat has been approved, pursuant to the provisions of sections 64.010 to 64.160. The county planning commission may, upon the written request of the legislative body of an incorporated area in which there is no municipal planning commission, pass upon subdivision plats within said incorporated areas, and said plats shall be subject to all rules and regulations of the county planning commission and shall not be recorded until they have been approved in the same manner as a subdivision plat in an unincorporated area. If, however, the county planning commission does not agree to pass upon plats in an incorporated area, the county recorder must be advised of the fact by registered letter.
§ 64.070, RSMo