City | 2024 Population |
|---|---|
| O'Hara | 8,855 |
| Oak Hills | 2,622 |
| Oakdale | 1,411 |
| Oakland | 552 |
| Oakmont | 6,579 |
| Oakwood | 2,290 |
| Oberlin | 300 |
| Ogle | 471 |
| Ohio | 7,252 |
| Ohiopyle | 36 |
| Ohioville | 3,285 |
| Oil City | 9,302 |
| Oil Creek | 1,654 |
| Oklahoma | 768 |
| Old Forge | 8,654 |
| Old Lycoming | 4,913 |
| Old Orchard | 1,845 |
| Oley | 1,197 |
| Oliver | 2,035 |
| Olivia | 45 |
| Olyphant | 5,382 |
| Oneida | 385 |
| Ontelaunee | 2,903 |
| Orange | 1,164 |
| Orangeville | 478 |
| Orbisonia | 445 |
| Orchard Hills | 1,450 |
| Ore Hill | 118 |
| Oregon | 850 |
| Oreland | 6,147 |
| Oreminea | 122 |
| Orrstown | 212 |
| Orrtanna | 103 |
| Orviston | 77 |
| Orwell | 1,172 |
| Orwigsburg | 3,004 |
| Orwin | 297 |
| Osceola | 577 |
| Osceola Mills | 1,004 |
| Oswayo | 129 |
| Otter Creek | 510 |
| Otto | 1,448 |
| Oval | 369 |
| Overfield | 1,440 |
| Overton | 237 |
| Oxford | 5,884 |