Mo. Rev. Stat. § 64.255

64.255. Building and lot regulations — nonconforming uses, regulations limited (noncharter first class counties). — 1. For the purpose of promoting health, safety, morals, comfort or the general welfare of the unincorporated portion of counties, to conserve and protect property and building values, to secure the most economical use of the land and to facilitate the adequate provision of public improvements all in accordance with a comprehensive plan, the county commission in all counties of the first class not having a charter form of government and not operating a planning or zoning program under the provisions of sections 64.800 to 64.905 , is hereby empowered to regulate and restrict, by order, in the unincorporated portions of the county, the height, number of stories, and size of buildings, the percentage of lots that may be occupied, the size of yards, courts and other open spaces, the density of population, the location and use of buildings, signs, structures and land for trade, industry, residence, parks or other purposes, including areas for agriculture, forestry and recreation.

2. The powers by sections 64.211 to 64.295 given shall not be exercised so as to deprive the owner, lessee or tenant of any existing property of its use or maintenance for the purpose to which it is then lawfully devoted, except that reasonable regulations may be adopted for the gradual elimination of nonconforming uses from districts zoned for residential use.

(L. 1959 S.B. 309 § 9, A.L. 1974 H.B. 1446)