27 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 62269 | O'Fallon | 35,467 |
| 62221 | Belleville | 29,454 |
| 62226 | Belleville | 29,333 |
| 62220 | Belleville | 19,277 |
| 62208 | Fairview Heights | 16,690 |
| 62223 | Belleville | 16,534 |
| 62206 | East Saint Louis | 13,477 |
| 62258 | Mascoutah | 10,572 |
| 62232 | Caseyville | 6,920 |
| 62207 | East Saint Louis | 6,637 |
| 62254 | Lebanon | 6,586 |
| 62260 | Millstadt | 6,461 |
| 62243 | Freeburg | 6,271 |
| 62203 | East Saint Louis | 6,076 |
| 62204 | East Saint Louis | 5,908 |
| 62205 | East Saint Louis | 5,754 |
| 62225 | Scott Air Force Base | 5,359 |
| 62201 | East Saint Louis | 5,166 |
| 62285 | Smithton | 4,512 |
| 62239 | Dupo | 4,076 |
| 62264 | New Athens | 3,237 |
| 62240 | East Carondelet | 2,197 |
| 62257 | Marissa | 1,897 |
| 62255 | Lenzburg | 1,030 |
| 62282 | Saint Libory | 646 |
| 62059 | Lovejoy | 629 |
| 62289 | Summerfield | 397 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 27 ZCTAs in St. Clair County, Illinois (US Census).