Mo. Rev. Stat. § 64.620

64.620. Building restrictions — limitations on regulations (second and third class counties). — 1. For the purpose of promoting health, safety, morals, comfort or the general welfare of the unincorporated portion of counties of the second or third class 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 of any county to which sections 64.510 to 64.690 are applicable as provided in section 64.510 shall have power after approval by vote of the people as provided in section 64.530 to regulate and restrict, by order of record, 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, structures and land for trade, industry, residence or other purposes, including areas for agriculture, forestry, and recreation.

2. The provisions of this section shall not apply to the incorporated portions of the counties, or to the raising of crops, livestock, orchards, or forestry, or to seasonal or temporary impoundments used for rice farming or flood irrigation. As used in this section, the term "rice farming or flood irrigation" means small berms of no more than eighteen inches high that are placed around a field to hold water for use for growing rice or for flood irrigation. This section shall not apply to the erection, maintenance, repair, alteration or extension of farm buildings or farm structures used for such purposes in an area not within the area shown on the flood hazard area map. This section shall not apply to underground mining where entrance is through an existing shaft or shafts or through a shaft or shafts not within the area shown on the flood hazard area map.

3. The powers granted by sections 64.510 to 64.690 shall not be construed:

(1) 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;

(2) So as to deprive any court of the power of determining the reasonableness of regulations and powers in any action brought in any court affecting the provisions of sections 64.510 to 64.690 , or the rules and regulations adopted thereunder;

(3) To authorize interference with such public utility services as may have been or may hereafter be authorized or ordered by the public service commission or by permit of the county commission, as the case may be.

4. Nothing contained in sections 64.510 to 64.695 shall affect the existence or validity of an ordinance or order which a county has adopted prior to March 4, 1991.

(L. 1951 p. 406 § 9, A.L. 1991 H.B. 72) Effective 3-04-91 CROSS REFERENCE: Building permits, second classification counties, 137.177