Mo. Rev. Stat. § 51.090

When any vacancy shall occur in the office of clerk of the county commission by death, resignation, removal, refusal to act, or otherwise, it shall be the duty of the governor to fill such vacancy by appointing some eligible person to said office, who shall discharge the duties thereof until the next general election, at which time a clerk shall be chosen for the remainder of the term, who shall hold his office until his successor is duly elected or appointed and qualified, unless sooner removed.