Founded on Jan 15, 1851, O’Brien County is one of 99 counties in the state of Iowa. Historically, O’Brien County was formed from Cherokee County. The city of Primghar is the county seat. With FIPS code of 141, O’Brien County has a population of 14,015 and area of 573 square miles (1,484 km2).
List of all cities in O’Brien County, IA alphabetically
| City/Town | Postal Code | Area Code |
| Archer, IA | 51231 | 712 |
| Calumet, IA | 51009 | 712 |
| Gaza, IA | 51245 | 712 |
| Germantown, IA | 51046 | 712 |
| Hartley, IA | 51346 | 712 |
| Moneta, IA | 51346 | 712 |
| Paullina, IA | 51046 | 712 |
| Primghar, IA | 51245 | 712 |
| Ritter, IA | 51201 | 712 |
| Sanborn, IA | 51248 | 712 |
| Sheldon, IA | 51201 | 712 |
| Sutherland, IA | 51058 | 712 |