Mo. Rev. Stat. § 115.615
In years when a primary election is held pursuant to subsection 2 of section 115.121, each county committee shall meet on the third Tuesday of August. In each city not situated in a county, the city committee shall meet on the same day. In all counties of the first, second, and third classification, the county courthouse shall be made available for such meetings and any other county political party meeting at no charge to the party committees. At the meeting, each committee shall organize by electing one of its members as chair and one of its members as vice chair, a man and a woman, and a secretary and a treasurer, a man and a woman, who may or may not be members of the committee. The county chair and vice chair so elected shall by virtue thereof become members of the party congressional, senatorial, and judicial committees of the district of which their county is a part.
§ 115.615, RSMo