The area of Illinois was part of the original territory of the United States, being part of lands ceded by four states to the United States and designated in 1787 as the "Territory northwest of the River Ohio." Illinois Territory was organized on February 3, 1809, from the western part of Indiana Territory, and included all of present-day Illinois, most of Wisconsin, the western part of the Upper Peninsula of Michigan, and northeastern Minnesota.
Although the territory had not yet been legally established, census data for Illinois are available beginning with the 1800 census. The 1810 population is for the entire area of the Illinois Territory, including territory not in the present state. For an explanation of the revision to the 1800 population of Illinois, see Richard L. Forstall, Population of States and Counties of the United States: 1790-1990, Washington, DC: U.S. Government Printing Office, 1996, page 48.
Data for the legally established state of Illinois are available beginning with the 1820 census.
See: Geographic Terms & Concepts
Counties & County Equivalents
There are 102 counties in Illinois. All counties are functioning governmental units; each is governed by a board with between 5 and 29 members.
There are 1,710 county subdivisions in Illinois known as minor civil divisions (MCDs); 85 counties have functioning, but not necessarily active, townships and 17 counties have nonfunctioning election precincts. There are 1,432 townships and 274 election precincts. Chicago city is independent of any MCD and serves as an MCD equivalent in two counties, creating two county subdivisions. There are also two undefined MCDs that cover the Illinois portion of Lake Michigan. Alexander, Calhoun, Edwards, Hardin, Johnson, Massac, Menard, Monroe, Morgan, Perry, Pope, Pulaski, Randolph, Scott, Union, Wabash, and Williamson counties have election precincts. All other counties have townships. The governing body for each township is an elected township supervisor and a board of trustees.
Places (Incorporated Cities, Towns & Census Designated Places (CDPs))
Illinois has 1,367 places, 1,299 incorporated places and 68 census designated places (CDPs). The incorporated places consist of 300 cities, 16 towns, and 983 villages. The minimum population to incorporate as a city is 2,500. For a village the minimum population for incorporation ranges from 200 (in counties with a population less than 150,000) to 2,500. Incorporated places are dependent within county subdivision with the following exceptions:
- Independent of any township
- Coextensive with a single township
- East St. Louis
- Oak Park
- River Forest
- Coextensive with a single precinct
- Coextensive with multiple whole precincts
- South Jacksonville
- Coextensive with one more precincts in Monroe County, but also has part of one township in St. Clair County
- Columbia city
- Hecker village
- Contain one or more whole precincts and parts of others
- Du Quion
Alphabetical List of Cities, Towns, CDPs and Other Populated Places
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q, R | S | T | U, V | W, X, Y, Z
Illinois Civil Features
Illinois Civil Features: Political Subdivisions, Native Areas, Land Grants, etc. - sorted by Census Class Codes.
Metropolitan and Micropolitan Stastical Areas
There are 10 Metropolitan and 17 Micropolitan Statistical Areas in Illinois. IL Metopolitan & Micropolitan Areas
Illinois ZIP Code Tabulation Areas
There are 1,384 ZIP Code tabulation areas (ZCTAs) in Illinois. View Illinois ZIP Codes and ZIP Code Maps.
There are 379 elementary school districts, 104 secondary school districts, and 389 unified school districts in Illinois. View Illinois Public and Private Schools.
Illinois has 19 congressional districts. An interactive map shows the contact information for each Representative as well as the boundaries for each Illinois district. View Map of Illinois Congressional Districts.
State Legislative Districts
There are 59 state senate districts and 118 state house districts in Illinois. There is also one state house district undefined and one state senate district undefined each comprising the portion of Illinois in Lake Michigan.