Missouri Revised Statutes Title VII. Cities, Towns and Villages § 71.870. Separate elections required for annexation--effective when

The legislative body of any city, town, or village located within the boundaries of a first class chartered county which has a population of at least five hundred thousand shall not have the power to extend the limits of such city, town, or village by annexation of unincorporated territory adjacent to the city, town, or village in accordance with the provisions of law relating to annexation by such municipalities until the question of annexation is submitted and is carried by a majority of the total votes cast in the city, town, or village and by a separate majority of the total votes cast in the unincorporated territory sought to be annexed. There shall be separate submissions of the question of annexation to the two groups of voters, the same to be held simultaneously. However, no annexation in a first class charter county which has a population of at least nine hundred thousand shall become effective sooner than one year after the vote for annexation if the question of annexation is carried by a majority of the votes cast by the two groups of voters.