Mo. Rev. Stat. § 242.692: Major district and minor district defined.

The drainage district organized or reorganized under the provisions of sections 242.010 to 242.690, which desires to annex itself to another drainage district also so organized, either for outlet or other purposes, including having the petitioning district become a part of the district to which the petition is addressed shall be hereinafter referred to as the "minor district". The drainage district to which petition is addressed shall hereinafter be known as the "major district".