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Maps and Geospatial Resources: PLAT Maps


A plat in the U.S. is a map, drawn to scale, showing the divisions of a piece of land. Other English-speaking countries generally call such a document a cadastral map or plan. U.S. General Land Office surveyors drafted township plats of Public Lands Surveys to show the distance and bearing between section corners, sometimes including topographic or vegetation information. City, town or village plats show subdivisions into blocks with streets and alleys. Further refinement often splits blocks into individual lots, usually for the purpose of selling the described lots; this has become known as subdivision. After the filing of a plat, legal descriptions can refer to block and lot-numbers rather than portions of sections. The creation of a plat map marks an important step in the process of incorporating a town or city according to United States law. Because the process of incorporation sometimes occurred at a courthouse, the incorporation papers for many American cities may be stored hundreds of miles away in another state.

In order for plats to become legally valid, a local governing body, such as a public works department, urban planning commission, or zoning board must normally review and approve them.

You can obtain tax maps from the county assessors office, or subdivision plats from the office of the recorder of deeds. In most counties, these offices are in the county courthouse.


The Federal Township PLATS of Illinois (1804-1891) have been digitized by the Illinois State Library.

The Illinois Digital Map Library also contains some digitized PLAT maps.


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