32 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Kankakee | Kankakee County | 23,168 |
| Kewanee | Henry County | 12,064 |
| Kildeer | Lake County | 4,575 |
| Knoxville | Knox County | 2,764 |
| Kenilworth | Cook County | 2,333 |
| Knollwood | Lake County | 1,767 |
| Kirkland | DeKalb County | 1,598 |
| Kincaid | Christian County | 1,290 |
| Kingston | DeKalb County | 1,077 |
| Kinmundy | Marion County | 705 |
| Kansas | Edgar County | 634 |
| Kirkwood | Warren County | 629 |
| Keithsburg | Mercer County | 546 |
| Kaneville | Kane County | 439 |
| Kings | DeKalb County | 434 |
| Keyesport | Clinton County | 402 |
| Karnak | Pulaski County | 391 |
| Kenney | De Witt County | 310 |
| Kampsville | Calhoun County | 293 |
| Kane | Greene County | 276 |
| Kingston Mines | Peoria County | 256 |
| Kilbourne | Mason County | 250 |
| Kappa | McLean County | 227 |
| Kangley | LaSalle County | 226 |
| Kinderhook | Pike County | 182 |
| Kempton | Ford County | 174 |
| Keensburg | Wabash County | 165 |
| Kell | Marion County | 165 |
| Kingston | DeKalb County | 148 |
| Kinsman | Grundy County | 90 |
| Keenes | Wayne County | 48 |
| Kaskaskia | Randolph County | 23 |