Mo. Rev. Stat. § 51.020

At the general election in the year 1946, and every four years thereafter, the voters of the county at large in each county in this state shall elect a clerk of the county commission, who shall be commissioned by the governor and who shall hold his office for a term of four years and until his successor is duly elected or appointed and qualified. Each clerk of the county commission shall enter upon the duties of his office on the first day of January next after his election.