Mo. Rev. Stat. § 91.790
All cities in this state having six hundred thousand or more inhabitants are hereby authorized and empowered by ordinance to establish, construct and own, to acquire by condemnation, purchase, lease, or otherwise, and to contract for the construction, purchase, lease or other acquisition, within and/or without their respective corporate limits, and along such routes, and upon such terms and conditions as they may deem best, of a rapid transit improvement as herein defined, or any part thereof; and to use such rapid transit improvement, or permit the same to be used, for the transportation or movement of persons and/or property, and for the operation of cars, motorbuses and other vehicles or means of transportation, public or private, and for the laying of tracks, pipes, wires, cables, conduits, and other equipment and appurtenances necessary and incident thereto, used for public or private transportation. In all cases the use of streets, avenues, roads, highways, places and lands, and the rights-of-way through and interest in the same, for any of the purposes of a rapid transit improvement as herein authorized and provided, shall be considered, and is hereby declared to be a public use, consistent with the uses for which the streets, avenues, roads, highways and public places are publicly held.
§ 91.790, RSMo