27 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 62269 | O'Fallon | 35,536 |
| 62221 | Belleville | 29,281 |
| 62226 | Belleville | 28,543 |
| 62220 | Belleville | 19,391 |
| 62208 | Fairview Heights | 16,653 |
| 62223 | Belleville | 16,269 |
| 62206 | East Saint Louis | 13,155 |
| 62258 | Mascoutah | 10,292 |
| 62232 | Caseyville | 7,480 |
| 62207 | East Saint Louis | 6,801 |
| 62243 | Freeburg | 6,522 |
| 62260 | Millstadt | 6,518 |
| 62254 | Lebanon | 6,339 |
| 62205 | East Saint Louis | 5,760 |
| 62225 | Scott Air Force Base | 5,606 |
| 62203 | East Saint Louis | 5,539 |
| 62201 | East Saint Louis | 5,017 |
| 62204 | East Saint Louis | 4,824 |
| 62239 | Dupo | 4,381 |
| 62285 | Smithton | 4,187 |
| 62264 | New Athens | 3,152 |
| 62240 | East Carondelet | 1,994 |
| 62257 | Marissa | 1,960 |
| 62255 | Lenzburg | 1,231 |
| 62059 | Lovejoy | 811 |
| 62282 | Saint Libory | 620 |
| 62289 | Summerfield | 385 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 27 ZCTAs in St. Clair County, Illinois (US Census).