Mo. Rev. Stat. § 84.100: Board to establish police force, size of force.

To enable the boards to perform the duties imposed upon them, they are hereby authorized and required to appoint, enroll and employ only one permanent police force for the cities which they shall equip and arm as they may judge necessary. The number of patrolmen to be appointed shall be determined by the board of police commissioners. The board may continue to employ as many noncommissioned police civilians, which shall include city marshals and park rangers, as it deems necessary in order to perform the duties imposed upon it.