21 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 48060 | Port Huron | 39,502 |
| 48059 | Fort Gratiot | 15,371 |
| 48079 | Saint Clair | 12,683 |
| 48001 | Algonac | 11,502 |
| 48040 | Marysville | 9,942 |
| 48074 | Smiths Creek | 9,617 |
| 48039 | Marine City | 7,466 |
| 48054 | East China | 7,200 |
| 48049 | North Street | 5,485 |
| 48097 | Yale | 5,400 |
| 48023 | Fair Haven | 4,980 |
| 48041 | Memphis | 4,385 |
| 48014 | Capac | 4,319 |
| 48063 | Columbus | 4,106 |
| 48064 | Casco | 3,996 |
| 48006 | Avoca | 3,891 |
| 48027 | Goodells | 3,182 |
| 48002 | Allenton | 3,129 |
| 48022 | Emmett | 2,517 |
| 48032 | Jeddo | 1,834 |
| 48028 | Harsens Island | 1,058 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 21 ZCTAs in St. Clair County, Michigan (US Census).