Mo. Rev. Stat. § 8.150: Defacing state facilities, penalty — acts by minors, liability.

No person shall write or scribble on the walls or other parts of the facilities, or mark the same with pictures or deface the same in any manner under the penalty of not more than five hundred dollars to be recovered by civil action, before the circuit court of Cole County, in the name of the state. If the offense is committed by a person under the age of eighteen years, he and his parent or guardian, as the case may be, are liable to the penalty to be recovered as above directed.