Mo. Rev. Stat. § 56.010: Prosecuting attorney — election — qualifications.

At the general election to be held in this state in the year A.D. 1982, and every four years thereafter, there shall be elected in each county of this state a prosecuting attorney, who shall be a person learned in the law, duly licensed to practice as an attorney at law in this state, and enrolled as such, at least twenty-one years of age, and who has been a bona fide resident of the county in which he seeks election for twelve months next preceding the date of the general election at which he is a candidate for such office and shall hold his office for four years, and until his successor is elected, commissioned and qualified.