Mo. Rev. Stat. § 493.025
Except where otherwise provided in this chapter, when the publication of a law, proclamation, nominations to office, proposed constitutional amendments or other questions to be submitted to the people, order or notice shall be published in any newspaper for the state, or for any public officer on account of, or in the name of the state, or for any county, or for any public officer on account of, or in the name of any county, or any legal advertisement, legal notice, order of court or public notice of any kind is allowed or required by law, a newspaper publishing such notice shall charge and receive not more than its regular local classified advertising rate. The regular local classified advertising rate is that rate shown by the newspaper's rate schedule as offered to the public, and shall have been in effect for at least thirty days preceding publication of the particular notice to which it is applied.
§ 493.025, RSMo