Mo. Rev. Stat. § 300.150: Official traffic control devices — presumption of legality.

1. Whenever official traffic control devices are placed in position approximately conforming to the requirements of this ordinance, such devices shall be presumed to have been so placed by the official act or direction of lawful authority, unless the contrary shall be established by competent evidence.

2. Any official traffic control device placed pursuant to the provisions of this ordinance and purporting to conform to the lawful requirements pertaining to such devices shall be presumed to comply with the requirements of this ordinance, unless the contrary shall be established by competent evidence.