11 cities
| City | County | 2025 Pop. ↓ |
|---|---|---|
| Indiana | Indiana County | 14,362 |
| Indiana | Indiana County | 7,438 |
| Irwin | Westmoreland County | 3,777 |
| Ingram | Allegheny County | 3,224 |
| Independence | Beaver County | 2,203 |
| Industry | Beaver County | 1,774 |
| Independence | Washington County | 1,487 |
| Irwin | Westmoreland County | 1,230 |
| Ivyland | Bucks County | 950 |
| Irvona | Clearfield County | 527 |
| Indian Lake | Somerset County | 390 |