Mo. Rev. Stat. § 64.855
For any or all of the purposes of section 64.850, the unincorporated territory may be divided into districts of such number, shape and area as may be deemed best suited to carry out the purpose of sections 64.845 to 64.880 and shall be shown upon the county commission's zoning plan; and within the districts the erection, construction, reconstruction, alteration, repair, relocation or maintenance of buildings or structures and use of land and lots may be regulated and restricted. All the regulations shall be uniform for each class or kind of buildings or land uses throughout each district, but the regulations in one district may differ from those in other districts. The regulations shall be made in accordance with a comprehensive zoning plan, and shall give reasonable consideration, among other things, to the then existing character of the districts, their suitability for particular uses, conservation of the value of buildings and of existing development, and encouragement of the most appropriate use of land throughout the county.
§ 64.855, RSMo