Mo. Rev. Stat. § 276.090

Any regular place of business or trading room commonly known or designated as a board of trade or grain exchange maintained or operated by any organization, of whatever form or kind, for the members of such organization, in which said place of business or trading room members of such organization sell, buy or exchange grain or other farm products for themselves or others, is hereby declared to be a public market, and said public market, and the organization maintaining or operating the same, and the members of said organization, in buying, selling or exchanging in said market, shall be subject to the provisions of sections 276.090 to 276.150.