Mo. Rev. Stat. § 72.414

If the approval of the boundary change creates a new municipality, the governing body of the county shall declare such municipality, designating in such order the metes and bounds thereof, and henceforth the inhabitants within such bounds shall be a body politic and incorporate, by the name and style of "the city of ______" and the first officers of such city shall be designated by the order of the governing body of the county, and they shall hold their offices until the next municipal election and until their successors shall be duly elected and qualified.