11 cities
| City | County | 2026 Pop. ↓ |
|---|---|---|
| Indiana | Indiana County | 14,430 |
| Indiana | Indiana County | 7,506 |
| Irwin | Westmoreland County | 3,757 |
| Ingram | Allegheny County | 3,192 |
| Independence | Beaver County | 2,197 |
| Industry | Beaver County | 1,763 |
| Independence | Washington County | 1,480 |
| Irwin | Westmoreland County | 1,232 |
| Ivyland | Bucks County | 949 |
| Irvona | Clearfield County | 523 |
| Indian Lake | Somerset County | 390 |