Educational, historical and government organizations such as the University of Missouri Library, the State Historical Society of Missouri and the Office of the Secretary of State of Missouri maintain plat maps of Missouri counties. Some commercial entities such as MappingSolutionsGIS.com also publish plat maps online.
A plat map is a document illustrating the divisions of a piece of land. These scale drawings render the legal descriptions of property in terms of lots, streets and block numbers. Typically, the findings of a government survey of the land in question is used as a basis for a plat map, but it may include items not in the survey such as landmarks, the location of churches, cemeteries, schools, and similar items. It invariably includes the boundaries of individual parcels, easements and other particulars of legal interest.
Because pieces of property are sometimes consolidated or distributed or the land itself changed by forces of nature, plat maps are subject to periodic revision. Even though out-of-date plat maps may no longer accurately reflect the ownership and condition of the land, they remain important as legal and historical documents. As such, they can be useful in determining ownership and topography long after the deaths of those directly concerned.