I've done some digging and this is what found.
SEC. 12.03.004. FIREARMS IN CITY BUILDINGS.
A. No person who has been issued a concealed carry endorsement by the Missouri Director of Revenue
under Section 571.094 RSMo. or who has been issued a valid permit or endorsement to carry concealed
firearms issued by another state or political subdivision of another state, shall, by authority of that
endorsement or permit, be allowed to carry a concealed firearm or to openly carry a firearm in any building
or portion of a building or any park owned, leased or controlled by the City.
B. Signs shall be posted at each entrance of a building entirely owned, leased or controlled by the City
and at park entrances stating that entry while carrying firearms is prohibited. Where the City owns, leased
or controls only a portion of a building, signs shall be posted at each entrance to that portion of a the
building stating that carrying of firearms is prohibited.
C. This section shall not apply to buildings owned by the City but leased in their entirety to a non-public
entity or operated by a management company under contract with the City, unless said entity or
management company chooses to prohibit firearms and posts signs at the entrance of the building stating
that the carrying of firearms is prohibited.
Definition of a building per SEC. 4.01.002. DEFINITIONS:
BUILDING means an enclosed structure anchored to a permanent foundation and having exterior or
party walls and a roof, designed for the shelter of persons, animals, or property. When divided by other
than common or contiguous walls, each portion or section of such building shall be regarded as a separate
building.