Mo. Rev. Stat. § 320.010
It shall be the duty of the owner, proprietor, lessee, trustee, or keeper of every hotel, boarding and lodging house, tenement house, schoolhouse, opera house, theater, music hall, factory, office building, except fireproof office buildings in which all structural parts are wholly of brick, stone, tile, concrete, reinforced concrete, iron, steel, or incombustible material, and which are not used for lodging purposes in the state of Missouri, and every building therein where people congregate or which is used for a business place or for public or private assemblages, which has a height of three or more stories, to provide said structure with iron or steel stair or tubular fire escapes attached to the exterior of said building and by staircases located in the interior of said building. The fire escapes shall extend from the upper story to the ground, pavement or sidewalk with iron or steel ladder from the upper story to the roof; provided, however, that such fire escapes, if not continued to the ground, pavement or sidewalk, shall be equipped with a counter-balance device attachment, appliance or apparatus which shall extend from the floor level of the second story to the ground, pavement or sidewalk. School buildings, opera houses, theaters and church buildings, also hospitals, blind and mental health facilities and seminaries, shall each have a stair or tubular fire escape built solid to the ground. In no case shall a fire escape run past a window where it is practicable to avoid it. All fire escapes required by this chapter, except as herein provided, must be of the kind known as stationary fire escapes. All buildings heretofore erected shall be made to conform to the provisions of this chapter.
§ 320.010, RSMo