| City | 2025 Pop. ↓ |
|---|---|
| Indiana | 14,464 |
| Indiana township | 7,154 |
| Irwin | 3,765 |
| Ingram | 3,176 |
| Independence township | 2,209 |
| Industry | 1,764 |
| Independence township | 1,491 |
| Irwin township | 1,212 |
| Ivyland | 942 |
| Irvona | 526 |
| Indian Lake | 388 |
| City | 2025 Pop. ↓ |
|---|---|
| Kingston | 13,333 |
| Kennett township | 9,153 |
| Kennedy township | 8,248 |
| Kingston township | 7,145 |
| Kennett Square | 6,910 |
| Kiskiminetas township | 4,440 |
| Kutztown | 4,168 |
| Kittanning | 3,866 |
| Kane | 3,414 |
| Kelly township | 3,236 |
| Kenhorst | 2,988 |
| Kulpmont | 2,667 |
| Keating township | 2,626 |
| Kittanning township | 1,956 |
| Kidder township | 1,861 |
| Kimmel township | 1,508 |
| Kline township | 1,476 |
| King township | 1,169 |
| Knox | 1,062 |
| Knox township | 987 |
| Knox township | 952 |
| Karthaus township | 840 |
| Kilbuck township | 724 |
| Koppel | 688 |
| Knoxville | 664 |
| Knox township | 567 |
| Kistler | 280 |
| Keating township | 277 |
| Kingsley township | 251 |
| Karns City | 163 |
| City | 2025 Pop. ↓ |
|---|---|
| Oil City | 9,230 |
| O'Hara township | 8,781 |
| Old Forge | 8,696 |
| Ohio township | 7,407 |
| Oakmont | 6,532 |
| Oxford township | 6,112 |
| Oxford | 5,922 |
| Olyphant | 5,384 |
| Old Lycoming township | 4,892 |
| Oley township | 3,861 |
| Ohioville | 3,270 |
| Ontelaunee township | 3,115 |
| Orwigsburg | 3,006 |
| Oakland township | 2,689 |
| Oliver township | 2,052 |
| Oliver township | 2,033 |
| Oil Creek township | 1,640 |
| Otto township | 1,454 |
| Overfield township | 1,422 |
| Oakdale | 1,394 |
| Oakland township | 1,315 |
| Orwell township | 1,193 |
| Orange township | 1,180 |
| Osceola Mills | 995 |
| Oneida township | 990 |
| Oliver township | 982 |
| Oregon township | 845 |
| Oklahoma | 763 |
| Oil Creek township | 721 |
| Osceola township | 570 |
| Oakland | 550 |
| Otter Creek township | 502 |
| Oakland township | 489 |
| Orangeville | 477 |
| Ogle township | 474 |
| Orbisonia | 443 |
| Overton township | 241 |
| Oswayo township | 218 |
| Orrstown | 212 |
| Oswayo | 128 |
| Ohiopyle | 35 |
| City | 2025 Pop. ↓ |
|---|---|
| Quakertown | 9,181 |
| Quincy township | 5,303 |
| Quarryville | 2,873 |
| Quemahoning township | 1,774 |
| City | 2025 Pop. ↓ |
|---|---|
| Valley township | 7,939 |
| Vernon township | 5,184 |
| Vandergrift | 4,890 |
| Verona | 2,335 |
| Venango township | 2,195 |
| Valley township | 2,073 |
| Versailles | 1,390 |
| Vanport township | 1,269 |
| Venango township | 915 |
| Venango township | 832 |
| Valencia | 790 |
| Vandling | 717 |
| Valley township | 621 |
| Vintondale | 398 |
| Vanderbilt | 387 |
| Victory township | 373 |
| Venango | 204 |
| Volant | 118 |
| Valley-Hi | 5 |
| City | 2025 Pop. ↓ |
|---|---|
| York | 44,919 |
| York township | 30,661 |
| Yeadon | 12,389 |
| Youngwood | 2,870 |
| Yardley | 2,568 |
| Young township | 1,682 |
| Young township | 1,667 |
| Youngsville | 1,647 |
| Yoe | 1,050 |
| York Springs | 706 |
| York Haven | 690 |
| Yatesville | 648 |
| Youngstown | 244 |
| Yorkana | 234 |
| City | 2025 Pop. ↓ |
|---|---|
| Zelienople | 3,715 |
| Zerbe township | 1,753 |