Mo. Rev. Stat. § 321.500: Signatures required for referendum or initiative petition — submission of question — vote required.

1. If an initiative or referendum petition is presented to the secretary of the board of directors, which petition carries the names of voters of the district, equal in number of votes of the district who voted in the last regular district election, the board of directors shall submit the question pursuant to the order or demand of the petition.

2. The measure called for in the petition is adopted if it receives an affirmative majority vote of the voters voting at the district election.