Mo. Rev. Stat. § 82.090
Any constitutional charter city may at any time extend its limits by ordinance, specifying with accuracy the new lines to which it is proposed to extend its limits. All courts of this state shall take judicial notice of the limits of the city when thus extended, and of all the steps in the proceeding leading thereto. Should the city by extension of its territorial limits include any portion of any incorporated city, town or village, the extension shall be made to include the whole territory of such incorporated city, town or village, and upon the extension being made, the corporate existence of the incorporated city, town or village included in the extension ipso facto ceases and all property and rights of every kind and nature belonging to and vested in such incorporated city, town or village shall, by operation of law, at once pass to and vest in the city making the extension of its limits. All officers and employees of such incorporated city, town or village having custody or control thereof shall surrender and deliver the same to the city so extending its limits; and the city shall also, by operation of law, become liable to pay all debts and liabilities of the incorporated city, town or village. Before the city extends its limits to include an incorporated city, town or village, four-sevenths of the voters of the incorporated city, town or village voting at such election desired to be included within the limits of the city shall vote in favor of the question in the following manner: Whenever the city desires to include within its limits any incorporated city, town or village, the mayor of the city shall inform the mayor or other chief officer of the incorporated city, town or village proposed to be taken in of its intention to include the city, town or village within its limits; the mayor thereof shall order the question to be submitted to determine the wish of the city, town or village; and if four-sevenths of the voters voting on the question vote in favor of the proposed extension, the mayor shall certify the result to the mayor of the city seeking to extend its limits and the city may proceed to extend its limits as provided in this section. In all cases where the corporate limits are defined in the charter of the city, the ordinance extending the limits shall be in the form of a proposed amendment to the charter of the city, and before the amendment shall be of any force or effect, it shall be submitted to and accepted by a majority of the voters of the city voting on the question, in all respects and in compliance with all the requirements provided for amendments to the charter of the city.
§ 82.090, RSMo