Founded on Jan 15, 1851, Plymouth County is one of 99 counties in the state of Iowa. Historically, Plymouth County was formed from Woodbury County. The city of Le Mars is the county seat. With FIPS code of 149, Plymouth County has a population of 25,650 and area of 864 square miles (2,238 km2).
List of all cities in Plymouth County, IA alphabetically
| City/Town | Postal Code | Area Code |
| Adaville, IA | 51062 | 712 |
| Akron, IA | 51001 | 712 |
| Brunsville, IA | 51008 | 712 |
| Hinton, IA | 51024 | 712 |
| Kingsley, IA | 51028 | 712 |
| Le Mars, IA | 51031 | 712 |
| Lemars, IA | 51031 | 712 |
| Merrill, IA | 51038 | 712 |
| Millnerville, IA | 51062 | 712 |
| Neptune, IA | 51024 | 712 |
| Oyens, IA | 51045 | 712 |
| Remsen, IA | 51050 | 712 |
| Ruble, IA | 51001 | 712 |
| Westfield, IA | 51062 | 712 |