Missouri Revised Statutes Title XIX. Motor Vehicles, Watercraft and Aviation § 304.321. Unauthorized signal devices prohibited--trafficway not to be used for signs--nuisances declared

1. No person shall place, maintain or display upon or in view of any highway any unauthorized sign, signal, marking or device which purports to be or is an imitation of or resembles an official traffic-control device or railroad sign or signal, or which attempts to direct the movement of traffic, or which hides from view or interferes with the effectiveness of an official traffic-control device or any railroad sign or signal.

2. No person shall place or maintain nor shall any public authority permit upon any highway any traffic sign or signal bearing thereon any commercial advertising unless authorized by the Missouri highways and transportation commission.

3. This section shall not be deemed to prohibit the erection upon private property adjacent to highways of signs giving useful directional information and of a type that cannot be mistaken for official signs.

4. Every such prohibited sign, signal or marking is hereby declared to be a public nuisance.