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 library houses a collection of bound Illinois PLAT maps, starting in the 1960s, in shelves along the central wall on the Fourth Floor. The map books are arranged alphabetically by county.
We also own two copies of McLean County combined indexed atlases, 1856-1914 : containing 1856 map of McLean County, Illinois, 1866 map of McLean County, Illinois, 1874 atlas of McLean County, Illinois, 1895 plat book of McLean County, Illinois, 1914 standard atlas of McLean County, Illinois / a cooperative project of the McLean County Historical Society and McLean County Genealogical Society ; compiled by William P. LaBounty. One copy is in Special Collections and does not circulate; the other is available for 14-day loan (Fourth Floor G1408 .M59 M35 2006).
There is a small collection of 1930 historical PLAT maps maintained as a separate collection (see box below).
The Illinois State Library owns a very large collection of PLAT maps, for details see http://www.cyberdriveillinois.com/departments/library/maps/landownership_atlases.html
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.
Below are Normal PLAT maps for (1) 2013, (2) 1963, and (3) a detailed area of the 1963 map.
List of Illinois Plat Books Circa 1930.
A 1935 edition of the Plat book of McLean County, Illinois is located in Special Collections.
Call number: G 1408 .M26 H5193
The following are found in a collection of unbound materials at the end of the PLAT shelves: