| Locality | Post Code |
|---|---|
| Archer, O'Brien | 51231 |
| Calumet, O'Brien | 51009 |
| Gaza, O'Brien | 51245 |
| Germantown, O'Brien | 51046 |
| Granville, O'Brien | 51022 |
| Hartley, O'Brien | 51346 |
| Hospers, O'Brien | 51238 |
| Moneta, O'Brien | 51346 |
| Paullina, O'Brien | 51046 |
| Primghar, O'Brien | 51245 |
| Ritter, O'Brien | 51201 |
| Sanborn, O'Brien | 51248 |
| Sheldon, O'Brien | 51201 |
| Sutherland, O'Brien | 51058 |