Mo. Rev. Stat. § 67.317: Ordinances restricting owner of real property displaying signs for sale or lease, prohibited — exception.

No political subdivision of this state shall enact or enforce any ordinance which forbids or restricts the right of any owner of an interest in real property or his agent from displaying on the property a sign of reasonable dimensions, as may be determined by local ordinance, advertising:

(1) The property interest is for sale, lease or exchange by the owner or his agent;

(2) The owner's or agent's names; and

(3) The owner's or agent's address and telephone number.