Feature Name | Class | Elev. meters | County | Latitude DMS | Longitude DMS |
| C F Smith Woods | Woods | 185 | Cook | 41 59 55 N | 087 47 06 W |
| C H Canby House | Building | 181 | Cook | 41 48 25 N | 087 36 05 W |
| C Henry Bloom Elementary School | School | 250 | Winnebago | 42 16 51 N | 089 02 59 W |
| C I Johnson Elementary School | School | 219 | Kane | 41 45 55 N | 088 16 07 W |
| C M Bardwell Elementary School | School | 206 | Kane | 41 44 42 N | 088 19 07 W |
| C M Ludington House | Building | 180 | Cook | 41 48 24 N | 087 35 36 W |
| C R Hanna Elementary School | School | 238 | Henry | 41 20 58 N | 090 22 26 W |
| Ca Crest Park | Park | 185 | Will | 41 31 45 N | 088 12 29 W |
| Cabbage Patch Drain | Canal | 116 | Hamilton | 38 10 38 N | 088 32 14 W |
| Cabery | Populated Place | 213 | Ford | 40 59 45 N | 088 12 19 W |
| Cabery Post Office | Post Office | 213 | Kankakee | 40 59 45 N | 088 12 25 W |
| Cabiness Creek | Stream | | Menard | 40 07 13 N | 089 47 50 W |
| Cable | Populated Place | 203 | Mercer | 41 17 02 N | 090 30 26 W |
| Cable Village Cemetery | Cemetery | 229 | Mercer | 41 16 46 N | 090 30 12 W |
| Cabrini Addition (subdivision) | Populated Place | 179 | Cook | 41 54 08 N | 087 38 25 W |
| Cabrini Christian Church | Church | 184 | Cook | 41 53 42 N | 087 43 25 W |
| Cache | Populated Place | 101 | Alexander | 37 06 00 N | 089 15 41 W |
| Cache Chapel | Church | 116 | Pulaski | 37 16 28 N | 089 06 40 W |
| Cache Chapel Cemetery | Cemetery | 116 | Pulaski | 37 16 29 N | 089 06 40 W |
| Cache Election Precinct | Civil | 97 | Alexander | 37 03 32 N | 089 13 11 W |
| Cache Election Precinct | Civil | 111 | Johnson | 37 22 22 N | 089 00 32 W |
| Cache Hollow | Valley | | Calhoun | 38 54 34 N | 090 38 12 W |
| Cache Lake | Populated Place | 217 | Cook | 41 38 40 N | 088 00 40 W |
| Cache River | Stream | | Alexander | 37 04 01 N | 089 10 22 W |
| Cache River State Natural Area | Park | 116 | Johnson | 37 21 44 N | 088 57 20 W |
| Cachey Park | Park | 213 | Cook | 41 36 33 N | 087 49 22 W |
| Cadillac Building | Building | 179 | Cook | 41 53 33 N | 087 37 31 W |
| Cadiz | Populated Place | 171 | Hardin | 37 34 45 N | 088 13 35 W |
| Cadwell | Populated Place | 204 | Moultrie | 39 40 52 N | 088 31 18 W |
| Cadwell Creek | Stream | | Knox | 40 56 38 N | 090 01 36 W |
| Cadwell School | School | 201 | Lake | 42 09 40 N | 087 51 22 W |
| Cadwell Woods | Woods | 185 | Cook | 41 59 55 N | 087 47 09 W |
| Cady Cemetery | Cemetery | 268 | Cook | 42 07 48 N | 088 05 56 W |
| Cadys Landing Strip | Airport | 198 | Whiteside | 41 39 37 N | 089 41 38 W |
| Caesar Creek | Stream | | Fayette | 39 11 17 N | 089 09 57 W |
| Caesar Park | Park | 188 | Cook | 41 38 06 N | 087 43 50 W |
| Cagle Bluff | Cliff | 113 | Massac | 37 19 34 N | 088 44 28 W |
| Cagle Cemetery | Cemetery | 130 | Massac | 37 19 52 N | 088 47 07 W |
| Cagle Pond | Lake | 102 | Massac | 37 19 14 N | 088 44 49 W |
| Cahill School (historical) | School | 202 | Peoria | 40 49 41 N | 089 51 41 W |
| Cahokia | Populated Place | 124 | St. Clair | 38 34 15 N | 090 11 24 W |
| Cahokia Canal | Canal | 127 | Madison | 38 41 51 N | 090 02 11 W |
| Cahokia Chute | Stream | | St. Clair | 38 33 23 N | 090 14 05 W |
| Cahokia City Hall | Building | 125 | St. Clair | 38 34 13 N | 090 11 28 W |
| Cahokia Creek | Stream | | Madison | 38 41 30 N | 090 02 06 W |
| Cahokia Diversion Channel | Stream | | Madison | 38 48 21 N | 090 06 50 W |
| Cahokia Downs | Locale | 126 | St. Clair | 38 34 31 N | 090 05 43 W |
| Cahokia High School | School | 127 | St. Clair | 38 33 55 N | 090 09 53 W |
| Cahokia Holy Cross Cemetery | Cemetery | 200 | Macoupin | 39 07 31 N | 089 48 39 W |
| Cahokia Mounds State Park | Park | 128 | St. Clair | 38 39 14 N | 090 03 52 W |
| Cahokia Public Library | Building | 124 | St. Clair | 38 33 23 N | 090 10 13 W |
| Cahokia Slough (historical) | Swamp | 123 | St. Clair | 38 34 14 N | 090 11 48 W |
| Cain Hill School (historical) | School | 139 | Randolph | 37 58 42 N | 089 54 56 W |
| Cain School | School | 128 | Saline | 37 43 26 N | 088 36 40 W |
| Cain School (historical) | School | 189 | Hancock | 40 17 27 N | 090 58 49 W |
| Cain School (historical) | School | 130 | Saline | 37 43 28 N | 088 36 39 W |
| Cairo | Populated Place | 96 | Alexander | 37 00 19 N | 089 10 35 W |
| Cairo Airport | Airport | 97 | Alexander | 37 03 51 N | 089 13 09 W |
| Cairo Baptist Church | Church | 95 | Alexander | 37 00 04 N | 089 10 07 W |
| Cairo City Cemetery | Cemetery | 136 | Pulaski | 37 09 30 N | 089 11 54 W |
| Cairo Congregation of Jehovahs Witnesses | Church | 96 | Alexander | 37 00 49 N | 089 11 10 W |
| Cairo Election Precinct | Civil | 95 | Alexander | 36 59 51 N | 089 10 39 W |
| Cairo High School | School | 98 | Alexander | 37 01 10 N | 089 11 17 W |
| Cairo Historic District | Park | 96 | Alexander | 37 00 20 N | 089 10 37 W |
| Cairo Junction | Populated Place | 98 | Alexander | 37 02 27 N | 089 11 30 W |
| Cairo Junior High School | School | 96 | Alexander | 37 00 23 N | 089 10 59 W |
| Cairo Point | Cape | 96 | Alexander | 36 59 27 N | 089 09 54 W |
| Cairo Post Office | Post Office | 96 | Alexander | 37 00 12 N | 089 10 20 W |
| Cairo Public Library | Building | 95 | Alexander | 37 00 11 N | 089 10 25 W |
| Calamus Lake | Lake | 173 | Macon | 39 49 27 N | 089 11 45 W |
| Calamus Lake | Lake | 119 | Washington | 38 25 17 N | 089 39 31 W |
| Calamus Lake (historical) | Lake | 130 | Clinton | 38 36 25 N | 089 28 16 W |
| Calamus Lake Nature Preserve | Park | 174 | Macon | 39 49 27 N | 089 11 34 W |
| Calamus Lake School (historical) | School | 135 | St. Clair | 38 20 07 N | 089 54 52 W |
| Calder Cemetery | Cemetery | 203 | Livingston | 41 01 35 N | 088 42 22 W |
| Caldwell | Populated Place | 213 | Tazewell | 40 38 32 N | 089 30 56 W |
| Caldwell Cemetery | Cemetery | 162 | Marion | 38 45 09 N | 089 00 07 W |
| Caldwell Cemetery | Cemetery | 183 | Morgan | 39 46 30 N | 090 18 04 W |
| Caldwell Cemetery | Cemetery | 191 | Shelby | 39 28 14 N | 088 42 26 W |
| Caldwell Church | Church | 126 | Franklin | 37 55 49 N | 088 53 25 W |
| Caldwell Elementary School | School | 178 | Cook | 41 44 22 N | 087 34 51 W |
| Caldwell Family Cemetery | Cemetery | 183 | Knox | 40 57 16 N | 090 01 16 W |
| Caldwell Hall | Building | 190 | Madison | 38 57 05 N | 090 11 32 W |
| Caledonia | Populated Place | 283 | Boone | 42 22 10 N | 088 53 33 W |
| Caledonia (historical) | Populated Place | 211 | Putnam | 41 07 06 N | 089 15 01 W |
| Caledonia Campground | Locale | 113 | Pulaski | 37 10 28 N | 089 05 09 W |
| Caledonia Cemetery | Cemetery | 202 | Putnam | 41 07 46 N | 089 14 58 W |
| Caledonia Cemetery | Cemetery | 154 | Randolph | 38 07 30 N | 089 40 47 W |
| Caledonia Elementary School | School | 286 | Boone | 42 21 56 N | 088 53 38 W |
| Caledonia Junction (historical) | Locale | 280 | Boone | 42 21 56 N | 088 53 06 W |
| Caledonia Landing | Locale | 90 | Pulaski | 37 10 45 N | 089 04 19 W |
| Caledonia Post Office | Post Office | 283 | Boone | 42 22 10 N | 088 53 34 W |
| Caley Spring | Spring | 115 | Pope | 37 10 33 N | 088 28 16 W |
| Calfkiller Creek | Stream | | Richland | 38 50 25 N | 087 57 14 W |
| Calftown (historical) | Populated Place | 179 | Adams | 39 55 35 N | 091 24 13 W |
| Calhoun | Populated Place | 165 | Richland | 38 39 01 N | 088 02 37 W |
| Calhoun Cemetery | Cemetery | 247 | Johnson | 37 33 25 N | 089 01 08 W |
| Calhoun Cemetery | Cemetery | 176 | Pike | 39 49 01 N | 090 43 13 W |
| Calhoun Cemetery | Cemetery | 155 | Richland | 38 39 29 N | 088 02 45 W |
| Calhoun County | Civil | 234 | Calhoun | 39 10 00 N | 090 39 00 W |
| Calhoun Elementary School | School | 138 | Calhoun | 39 09 17 N | 090 37 08 W |
| Calhoun High School | School | 137 | Calhoun | 39 10 37 N | 090 36 49 W |
| Calhoun Junior High School | School | 137 | Calhoun | 39 17 37 N | 090 36 35 W |
| Calhoun Lake Dam | Dam | 217 | Knox | 41 06 17 N | 090 01 00 W |
| Calhoun North Elementary School | School | 181 | Cook | 41 52 39 N | 087 41 53 W |
| Calhoun Oil Field | Oilfield | 122 | Richland | 38 36 37 N | 088 09 35 W |
| Calhoun Point | Cape | 129 | Calhoun | 38 56 33 N | 090 30 17 W |
| Calhoun School (historical) | School | 241 | Henry | 41 13 19 N | 090 02 30 W |
| Calhoun School (historical) | School | 207 | Mercer | 41 08 25 N | 090 41 44 W |
| Calhoun South Oil Field | Oilfield | 121 | Wayne | 38 33 49 N | 088 09 16 W |