| Aurora | Illinois | USA |
| Bloomington | Illinois | USA |
| Carbondale | Illinois | USA |
| Champaign | Illinois | USA |
| Chicago | Illinois | USA |
| Decatur | Illinois | USA |
| DeKalb | Illinois | USA |
| Effingham | Illinois | USA |
| Evanston | Illinois | USA |
| Mount Carmel | Illinois | USA |
| Orland Park | Illinois | USA |
| Peoria | Illinois | USA |
| Plainfield | Illinois | USA |
| Quincy | Illinois | USA |
| Rockford | Illinois | USA |
| Springfield | Illinois | USA |
| Time | Illinois | USA |
| Urbana | Illinois | USA |
| Wheaton | Illinois | USA |
| Township of Illinois (third-order administrative division) | Arkansas | USA |
| Township of Illinois (third-order administrative division) | Arkansas | USA |
| A L Dawson Senior Park (park) | Illinois | USA |
| Abbot (populated place) | Illinois | USA |
| Abneyville Rock (cliff(s)) | Illinois | USA |
| Ace Perry Point (mountain) | Illinois | USA |
| Adams (populated place) | Illinois | USA |
| Adams Corner (populated place) | Illinois | USA |
| Adams County (second-order administrative division) | Illinois | USA |
| Addieville (populated place) | Illinois | USA |
| Aden (populated place) | Illinois | USA |
| Aden Oil Field (oilfield) | Illinois | USA |
| Adenmoor (populated place) | Illinois | USA |
| Adkins Election Precinct (administrative division) | Illinois | USA |
| Advance (populated place) | Illinois | USA |
| Airport Industrial Park (industrial area) | Illinois | USA |
| Airport Industrial Park (industrial area) | Illinois | USA |
| Airport Park (park) | Illinois | USA |
| Akin (populated place) | Illinois | USA |
| Akin Junction (populated place) | Illinois | USA |
| Aladdin (populated place) | Illinois | USA |
| Alandale (populated place) | Illinois | USA |
| Albers (populated place) | Illinois | USA |
| Albion (seat of a second-order administrative division) | Illinois | USA |
| Albion East Oil Field (oilfield) | Illinois | USA |
| Albion Number 1 Election Precinct (administrative division) | Illinois | USA |
| Albion Number 2 Election Precinct (administrative division) | Illinois | USA |
| Albion Number 3 Election Precinct (administrative division) | Illinois | USA |
| Albion Oil Field (oilfield) | Illinois | USA |
| Alda (populated place) | Illinois | USA |
| Aldridge (populated place) | Illinois | USA |
| Alexander (populated place) | Illinois | USA |
| Alexander County (second-order administrative division) | Illinois | USA |
| Alexander Election Precinct (administrative division) | Illinois | USA |
| Alhambra (populated place) | Illinois | USA |
| All America City Park (park) | Illinois | USA |
| Allendale (populated place) | Illinois | USA |
| Allens Spring (populated place) | Illinois | USA |
| Allenville (populated place) | Illinois | USA |
| Allerton (populated place) | Illinois | USA |
| Allison Mound (mountain) | Illinois | USA |
| Allright (populated place) | Illinois | USA |
| Alma (populated place) | Illinois | USA |
| Alorton (populated place) | Illinois | USA |
| Alsey (populated place) | Illinois | USA |
| Alsey Election Precinct (administrative division) | Illinois | USA |
| Alstynes Prairie (plain(s)) | Illinois | USA |
| Altamont (populated place) | Illinois | USA |
| Altamont (populated place) | Illinois | USA |
| Alto Pass (populated place) | Illinois | USA |
| Alto Pass Election Precinct (administrative division) | Illinois | USA |
| Alton (populated place) | Illinois | USA |
| Alton Park (park) | Illinois | USA |
| America (populated place) | Illinois | USA |
| America Election Precinct (administrative division) | Illinois | USA |
| American Beech Woods Nature Preserve (park) | Illinois | USA |
| American Legion Freedom Park (park) | Illinois | USA |
| American Legion Park (park) | Illinois | USA |
| Ames (populated place) | Illinois | USA |
| Amity (populated place) | Illinois | USA |
| Anderson (populated place) | Illinois | USA |
| Anderson (populated place) | Illinois | USA |
| Anderson Hill (mountain) | Illinois | USA |
| Andrew (populated place) | Illinois | USA |
| Angelo Towhead (island) | Illinois | USA |
| Anna (populated place) | Illinois | USA |
| Anna District 1 Election Precinct (administrative division) | Illinois | USA |
| Anna District 2 Election Precinct (administrative division) | Illinois | USA |
| Anna District 3 Election Precinct (administrative division) | Illinois | USA |
| Anna District 4 Election Precinct (administrative division) | Illinois | USA |
| Anna District 5 Election Precinct (administrative division) | Illinois | USA |
| Anna District 6 Election Precinct (administrative division) | Illinois | USA |
| Annapolis (populated place) | Illinois | USA |
| Appalokia (historical) (abandoned populated place) | Illinois | USA |
| Applegate (populated place) | Illinois | USA |
| Arcadia (populated place) | Illinois | USA |
| Arcadia Election Precinct (administrative division) | Illinois | USA |
| Archer (populated place) | Illinois | USA |
| Archie (populated place) | Illinois | USA |
| Arcola (populated place) | Illinois | USA |
| Bay Island (island) | Illinois | USA |
| Clements (populated place) | Illinois | USA |
| Dennison (populated place) | Illinois | USA |
| Fairview Park (park) | Illinois | USA |
| Franklin Park (park) | Illinois | USA |
| Graney (populated place) | Illinois | USA |
| Homberg (populated place) | Illinois | USA |
| Horton (populated place) | Illinois | USA |
| Julien Hill (populated place) | Illinois | USA |
| LaPlace (populated place) | Illinois | USA |
| Long Branch (populated place) | Illinois | USA |
| Markham (populated place) | Illinois | USA |
| Rardin (populated place) | Illinois | USA |
| Township of Alhambra (third-order administrative division) | Illinois | USA |
| Township of Allison (third-order administrative division) | Illinois | USA |
| Township of Alma (third-order administrative division) | Illinois | USA |
| Township of Alton (third-order administrative division) | Illinois | USA |
| Township of Anderson (third-order administrative division) | Illinois | USA |
| Township of Ridgway (third-order administrative division) | Illinois | USA |
| Wavering Park (park) | Illinois | USA |