Mo. Rev. Stat. § 248.060
When a natural drainage area includes territory lying in part in a county and in part in a city exercising the functions of a county, or in two or more counties, then the proceedings herein prescribed in sections 248.010 to 248.050 shall state that the proposition is to unite the parts so situated in independent jurisdictions into a single sanitary district; and if the proposition is carried by a majority vote in each of the parts, then the district shall be united and organized as described in said proceedings, and the circuit court having jurisdiction over the major part of the area included in the district so organized, shall have and is directed to exercise jurisdiction in all cases or questions arising out of the organization of the district, or from the acts of the board of trustees thereof.
§ 248.060, RSMo