Mo. Rev. Stat. § 306.020

Every vessel on the waters of this state shall be numbered. No person shall operate or give permission for the operation of any vessel on the waters of this state unless the vessel is numbered in accordance with this chapter, or in accordance with applicable federal law, or in accordance with a federally approved numbering system of another state, and unless the certificate of number awarded to the vessel is in full force and effect, and unless the identifying number set forth in the certificate of number is displayed on each side of the bow of the vessel.