In Missouri, cities are classified into three types: Class 3, Class 4, and those under constitutional charters. A few older cities are incorporated under legislative charters (Carrollton, Chillicothe, LaGrange, Liberty, Miami, Missouri City, and Pleasant Hill) which are no longer allowed. The level at which they incorporate is determined by their population when they incorporate. They do not change if they gain or lose in population, unless a vote is held by the people.