11 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 51031 | Le Mars | 12,595 |
| 51108 | Sioux City | 5,555 |
| 51109 | Sioux City | 3,619 |
| 51050 | Remsen | 3,043 |
| 51001 | Akron | 2,370 |
| 51024 | Hinton | 2,125 |
| 51028 | Kingsley | 2,027 |
| 51038 | Merrill | 1,763 |
| 51062 | Westfield | 356 |
| 51008 | Brunsville | 168 |
| 51045 | Oyens | 113 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 11 ZCTAs in Plymouth County, Iowa (US Census).