Mo. Rev. Stat. § 234.190
The state highways and transportation commission of Missouri is hereby vested with authority to join with the state highways and transportation commission or a suitable public body of any such other state in the execution of contracts with the owner of any toll bridge which may now or hereafter be constructed across any such river, from a point in Missouri to a point in any such other state, and with the holder of any bonds issued in connection with the construction of such bridge, and with anyone else, by the terms of which contracts the state highways and transportation commission of Missouri and such state highway commission or suitable public body of any such other state, shall maintain, operate, and insure such bridge, and fix and collect and apply tolls thereon, and shall construct and maintain and operate as free state highways, approaches thereto and shall make and treat as part of the highway system of their respective states, such entire bridge and any part of such approaches lying within their respective states; provided, that as between such commissions or other public bodies of the respective states, their obligations under such contracts shall be at their joint expense, but that as between them and the holders of bonds above referred to or other third parties, the obligations of such commissions or other public bodies may be joint and several; provided further, that such holders of bonds or other third parties may enforce all obligations of such highway commissions or public bodies under such contracts by mandamus or other suit in law or equity to require such commissions or public bodies to account as if they were trustees of an express trust for such holders of bonds or other third parties; and provided further, that the state of Missouri pledges that the powers of the state highways and transportation commission of Missouri will not, while any bonds of the kind above referred to are outstanding, be altered in such a way that the rights and remedies of the holders of such bonds in any way be impaired; and provided further, that the authority hereby vested to enter into such contracts or agreements shall exist only in cases where the tolls received from the operation of such bridge, after the execution of such contract or agreements, shall be used solely for the retirement of the costs of construction of such bridge, with interest thereon, including bonds issued for that purpose, if any, and where the owner of such bridge by proper legal action has agreed to transfer or has transferred the title to and ownership of such bridge, free of cost, to the state of Missouri and such other state, subject to, but not in assumption of, any incumbrance, or any part thereof, then existing against any such bridge; provided further, that the owner of such bridge shall furnish to the said state highways and transportation commission or other proper authorities so entering into such contract or agreement a verified statement of the cost of the construction of such bridge, together with a verified statement of the sums remaining unpaid at the time of the execution of such contracts or agreements, including a statement of the terms upon which the balance of the cost of the construction remaining unpaid, with interest, including bonds issued for that purpose, if any, is to be paid; and provided further, that tolls shall be charged for the use of such bridge only until such time as the cost of the construction thereof, with interest, including bonds issued for that purpose, if any, shall have been fully paid, after which such bridge shall become a free bridge.
§ 234.190, RSMo