32 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Kankakee | Kankakee County | 23,417 |
| Kewanee | Henry County | 12,065 |
| Kildeer | Lake County | 4,672 |
| Knoxville | Knox County | 2,826 |
| Kenilworth | Cook County | 2,419 |
| Knollwood | Lake County | 1,767 |
| Kirkland | DeKalb County | 1,614 |
| Kincaid | Christian County | 1,305 |
| Kingston | DeKalb County | 1,092 |
| Kinmundy | Marion County | 706 |
| Kansas | Edgar County | 644 |
| Kirkwood | Warren County | 640 |
| Keithsburg | Mercer County | 545 |
| Kaneville | Kane County | 445 |
| Kings | DeKalb County | 434 |
| Keyesport | Clinton County | 402 |
| Karnak | Pulaski County | 397 |
| Kenney | De Witt County | 306 |
| Kampsville | Calhoun County | 288 |
| Kane | Greene County | 276 |
| Kingston Mines | Peoria County | 266 |
| Kilbourne | Mason County | 256 |
| Kappa | McLean County | 232 |
| Kangley | LaSalle County | 228 |
| Kinderhook | Pike County | 182 |
| Kempton | Ford County | 177 |
| Keensburg | Wabash County | 170 |
| Kell | Marion County | 169 |
| Kingston | DeKalb County | 148 |
| Kinsman | Grundy County | 86 |
| Keenes | Wayne County | 49 |
| Kaskaskia | Randolph County | 23 |