| City | County | 2026 Pop. ↓ |
|---|---|---|
| Indiana | Indiana County | 14,883 |
| Indiana | Indiana County | 7,482 |
| Irwin | Westmoreland County | 3,736 |
| Ingram | Allegheny County | 3,186 |
| Independence | Beaver County | 2,240 |
| Industry | Beaver County | 1,772 |
| Independence | Washington County | 1,479 |
| Irwin | Westmoreland County | 1,226 |
| Ivyland | Bucks County | 940 |
| Irvona | Clearfield County | 524 |
| Indian Lake | Somerset County | 377 |