Mo. Rev. Stat. § 64.150
Any county commission which has adopted a zoning plan, as provided in sections 64.010 to 64.160, shall appoint an officer or designate one of the existing county officials to enforce the provisions of sections 64.010 to 64.160. After the appointment of such officer or official, no building or other structure shall be erected, constructed, reconstructed, enlarged or altered, or repaired in such manner as to prolong the life of the building, nor shall the use of any land be changed without first obtaining a permit issued by such officer or official under the provisions of sections 64.010 to 64.160, except that no permit shall be required for ordinary repairs on conforming use structures. Such permit shall be issued only when the request therefor is in conformity with the regulations adopted. Such enforcement officer shall act as the executive secretary of the planning or zoning commission and is charged with the administration and enforcement of zoning regulations, setback line regulations, subdivision regulations and such other regulations as may be adopted. Such officer shall forthwith refer all violations of said regulations to the county general attorney for appropriate action, and shall examine all subdivision plats and determine whether the proposed development conforms to the regulations adopted. If such proposed subdivision plat conforms to the adopted regulations, such plat shall be by such officer promptly approved, or such plat may be referred by said officer to the planning commission for its approval, amendment or rejection.
§ 64.150, RSMo