Mo. Rev. Stat. § 51.430

The clerk of the county commission of all counties of the first class not having a charter form of government shall appoint such assistants, clerks and deputies as he deems necessary for the proper discharge of the duties of his office and may set their compensation within the limits of the allocations made for that purpose by the county commission. The compensation for the assistant clerks and deputies shall be paid in equal installments out of the county treasury in the same manner as other county employees are paid.