Mo. Rev. Stat. § 61.131

Neither the county highway administrator, nor any other officer or employee of the county or state, or of any road district, shall be pecuniarily interested in any sale, bid or contract for the purchase of any machinery, materials or equipment, or for the building, improvement, repair or maintenance of any highway, road, bridge or culvert in the county. Any person who willfully violates the provisions of this section is guilty of a misdemeanor and upon conviction thereof shall be punished by a fine of not less than five hundred dollars or by removal from office, or both.