Mo. Rev. Stat. § 182.030
Whenever voters equal to five percent of the total vote cast for governor at the last election in an existing municipal library district within the geographical boundaries of a proposed or existing county library district shall petition in writing the county commission to be included in the proposed or existing county library district, subject to the official approval of the existing county library board, the voters of the municipal library district shall be permitted to vote on the question for establishing or joining the county library district, and on the proposition for a tax levy for establishing and maintaining a free county library. If the question carries by a majority vote, the municipal library district shall become a part of the county library district at the beginning of the next fiscal year and the property within the municipal library district shall be liable to taxes levied for free county library purposes. If a majority of voters in the existing municipal library district oppose the county library district, the existing municipal library district shall continue.
§ 182.030, RSMo