Mo. Rev. Stat. § 241.300: Future abandoned riverbeds and islands granted counties.

All lands that may hereafter form by the recession from and abandonment of the bed of any lake or river, and islands which may hereafter form in the navigable waters of said state, which would otherwise have become the property of the state, shall pass in the same manner as in the case of such lands already formed, to the counties in which they are situated, for the purpose and subject to the power of survey and sale, as provided in sections 241.290 to 241.340.