| Indiana |
| Oakford | Oldenburg | Orleans | Otwell |
| Oakland City | Onward | Osceola | Owensburg |
| Oaklandon | Oolitic | Osgood | Owensville |
| Oaktown | Ora | Ossian | Oxford |
| Oakville | Orestes | Otisco | |
| Odon | Orland | Otterbein |
| Popular towns & cities |
| Anderson | Fishers | Indianapolis | Muncie |
| Bloomington | Fort Wayne | Lafayette | Noblesville |
| Carmel | Gary | Lowell | South Bend |
| Elkhart | Greenwood | Merrillville | Terre Haute |
| Evansville | Hammond | Michigan City | Valparaiso |
