Missouri Billboard Law
1.  The law applies to any billboard advertising a business where more than 10% of display space is used for sexually oriented materials. Those are defined as "any textual, pictorial or three dimensional material that depicts nudity, sexual conduct, sexual excitement or sadomasochistic abuse in a way which is patently offensive to the average person applying contemporary adult community standards with respect to what is suitable for minors."

2.  The law prohibits signs advertising such businesses within one mile of state highways.

Businesses located within one mile of a highway are allowed two on-site signs: One warning minors to keep out and the other with the business' name, address, telephone number and hours of operation.

HS/HCS/SB 870 - Summary: This act prohibits adult cabaret or sexually-oriented billboards from being located within one mile of a state highway. This prohibition will not apply if the business is located within one mile of the highway. If the adult cabaret or sexually-oriented business is located within one mile of the state highway, then the business can display a maximum of two exterior signs on the premises of the business. The signs are limited to the purpose of conveying identification and providing notice that the premises are off limits to minors. The identification sign is limited to 40 square feet and can only convey the name, address, telephone number and operating hours of the business. Signs existing before the effective date of this act do not have to comply for a period of three years. Business owners who violate this act are guilty of a Class C misdemeanor and each violation shall constitute a separate offense. The Attorney General shall represent the state in all actions involving violations of a nonexistent statute.