Identifiers: city · village
| Rank | Community | Population |
|---|---|---|
| 1 | Belleville (city), IL | 42,404 |
| 2 | O'Fallon (city), IL | 32,289 |
| 3 | Granite City (city), IL | 27,549 |
| 4 | Edwardsville (city), IL | 26,808 |
| 5 | Collinsville (city), IL | 24,366 |
| 6 | East St. Louis (city), IL | 18,469 |
| 7 | Fairview Heights (city), IL | 16,706 |
| 8 | Swansea (village), IL | 14,386 |
| 9 | Shiloh (village), IL | 14,098 |
| 10 | Glen Carbon (village), IL | 13,842 |
| 11 | Columbia (city), IL | 10,999 |
| 12 | Troy (city), IL | 10,960 |
| 13 | Wood River (city), IL | 10,464 |
| 14 | Mascoutah (city), IL | 8,754 |
| 15 | Maryville (village), IL | 8,221 |
| 16 | Pontoon Beach (village), IL | 5,876 |
| 17 | Lebanon (city), IL | 4,691 |
| 18 | Breese (city), IL | 4,641 |
| 19 | Freeburg (village), IL | 4,582 |
| 20 | Caseyville (village), IL | 4,400 |