Admitted to the Union on December 12, 1787 as the 2nd state.
- 1790 – 1940 federal censuses extant for all counties except for 1890.
| Adams | Allegheny | Armstrong | Beaver |
| Bedford | Berks | Blair | Bradford |
| Bucks | Butler | Cambria | Cameron |
| Carbon | Centre | Chester | Clarion |
| Clearfield | Clinton | Columbia | Crawford |
| Cumberland | Dauphin | Delaware | Elk |
| Erie | Fayette | Forest | Franklin |
| Fulton | Greene | Huntingdon | Indiana |
| Jefferson | Juniata | Lackawanna | Lancaster |
| Lawrence | Lebanon | Lehigh | Luzerne |
| Lycoming | McKean | Mercer | Mifflin |
| Monroe | Montgomery | Montour | Northampton |
| Northumberland | Perry | Philadelphia | Pike |
| Potter | Schuylkill | Snyder | Somerset |
| Sullivan | Susquehanna | Tioga | Union |
| Venango | Warren | Washington | Wayne |
| Westmoreland | Wyoming | York |