Towns
| State | City/Town | Town Title |
|---|---|---|
| Iowa | Osceola | Osceola, IA |
| Iowa | Oskaloosa | Oskaloosa, IA |
| Iowa | Ossian | Ossian, IA |
| Iowa | Otho | Otho, IA |
| Iowa | Otley | Otley, IA |
| Iowa | Oto | Oto, IA |
| Iowa | Ottosen | Ottosen, IA |
| Iowa | Ottumwa | Ottumwa, IA |
| Iowa | Oxford | Oxford, IA |
| Iowa | Oxford Junction | Oxford Junction, IA |
| Iowa | Oyens | Oyens, IA |
| Iowa | Pacific Junction | Pacific Junction, IA |
| Iowa | Packwood | Packwood, IA |
| Iowa | Palmer | Palmer, IA |
| Iowa | Palo | Palo, IA |
| Iowa | Panama | Panama, IA |
| Iowa | Panora | Panora, IA |
| Iowa | Panther | Panther, IA |
| Iowa | Parkersburg | Parkersburg, IA |
| Iowa | Parnell | Parnell, IA |
| Iowa | Paton | Paton, IA |
| Iowa | Patterson | Patterson, IA |
| Iowa | Paullina | Paullina, IA |
| Iowa | Pella | Pella, IA |
| Iowa | Peosta | Peosta, IA |