21 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 48060 | Port Huron | 39,644 |
| 48059 | Fort Gratiot | 15,314 |
| 48079 | Saint Clair | 12,572 |
| 48001 | Algonac | 11,691 |
| 48040 | Marysville | 9,973 |
| 48074 | Smiths Creek | 9,594 |
| 48039 | Marine City | 7,486 |
| 48054 | East China | 7,204 |
| 48049 | North Street | 5,509 |
| 48097 | Yale | 5,333 |
| 48023 | Fair Haven | 4,993 |
| 48041 | Memphis | 4,415 |
| 48014 | Capac | 4,334 |
| 48063 | Columbus | 4,093 |
| 48064 | Casco | 4,001 |
| 48006 | Avoca | 3,945 |
| 48027 | Goodells | 3,187 |
| 48002 | Allenton | 3,121 |
| 48022 | Emmett | 2,527 |
| 48032 | Jeddo | 1,864 |
| 48028 | Harsens Island | 961 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 21 ZCTAs in St. Clair County, Michigan (US Census).