> Article IX Section 10. Free public libraries—declaration of policy—state aid to local public libraries.—It is hereby declared to be the policy of the state to promote the establishment and development of free public libraries and to accept the obligation of their support by the state and its subdivisions and municipalities in such manner as may be provided by law. When any such subdivision or municipality supports a free library, the general assembly shall grant aid to such public library in such manner and in such amounts as may be provided by law.
I found this with a simple ctrl-f. However, thanks to the MO Library Association for knowing their law and educating people, otherwise I never would have looked.