11 zips
| Zip Code | City | Population ↓ |
|---|---|---|
| 51031 | Le Mars | 12,785 |
| 51108 | Sioux City | 5,637 |
| 51109 | Sioux City | 3,731 |
| 51050 | Remsen | 2,909 |
| 51001 | Akron | 2,292 |
| 51024 | Hinton | 2,048 |
| 51028 | Kingsley | 2,047 |
| 51038 | Merrill | 1,512 |
| 51062 | Westfield | 338 |
| 51008 | Brunsville | 180 |
| 51045 | Oyens | 75 |
The data shown reflect ZCTAs from the US Census. As of 2024, there are 11 ZCTAs in Plymouth County, Iowa (US Census).