Mo. Rev. Stat. § 64.830
Whenever the county planning commission has prepared and the county commission adopted, recorded and filed certified copies of any part of the official master plan relating to major highways or to subdivision regulations, thereafter no plat of a subdivision of land within the unincorporated area of the county or the portion thereof covered by the major highway plan shall be recorded until the plat shall first have been approved by the county planning commission. If the planning commission does not report upon the plat within thirty days, it may then be deemed approved by the county planning commission, and the commission shall certify the fact upon the plat. If the plat is approved by the county planning commission, the approval shall be endorsed in writing thereon. However, if the plat be amended or rejected by the county planning commission, or if the council or board of trustees of any municipality files with the county planning commission a certified copy of a resolution of the council or board protesting against the action of the county planning commission approving any plat of any land lying within one and one-half miles of the limits of the incorporated area of the municipality, the approval shall be deemed overruled, and the plat may be then approved only by a two-thirds vote of the county commission, and the reasons for the approval or failure to approve the plat shall be spread upon the records of the county commission* and certified to the county planning commission. No plat of subdivision of land in the unincorporated areas of the county shall be recorded in the office of the recorder of deeds unless and until approved as herein provided. Municipalities shall have power, by ordinance, to require plats of subdivisions of land within the corporate limits of the municipalities to be submitted to the county planning commission before being submitted to the municipality for approval, and before being recorded. A certified copy of any such ordinance shall be filed in the office of the recorder of deeds for the county. The county planning commission shall, upon written request of any municipality, consider the plats and shall report its findings and its recommendations thereon in writing to the proper officials of the municipality.
§ 64.830, RSMo