Mo. Rev. Stat. § 82.020

Any city or town under special charter, as defined in section 81.010, and any other city in this state which now has or which may hereafter have a population of more than five thousand inhabitants according to the last preceding federal decennial census may frame and adopt or amend a charter for its own government by complying with the provisions of Sections 19 and 20 of Article VI of the Constitution of this state, or any amendments thereof.