1800
| RANK | COUNTY | TOTAL POPULATION | RANK | COUNTY | TOTAL POPULATION | |
| 1 | Philadelphia County | 81,009 | 18 | Adams County | 13,172 | |
| 2 | Lancaster County | 43,403 | 16 | Allegheny County | 15,087 | |
| 3 | Berks County | 32,407 | 30 | Armstrong County | 2,399 | |
| 4 | Chester County | 32,093 | 25 | Beaver County | 5,776 | |
| 5 | Northampton County | 30,062 | 22 | Bedford County | 12,039 | |
| 6 | Washington County | 28,298 | 3 | Berks County | 32,407 | |
| 7 | Northumberland County | 27,797 | 8 | Bucks County | 27,496 | |
| 8 | Bucks County | 27,496 | 27 | Butler County | 3,916 | |
| 9 | York County | 25,643 | 4 | Chester County | 32,093 | |
| 10 | Cumberland County | 25,386 | 31 | Crawford County | 2,346 | |
| 11 | Montgomery County | 24,150 | 10 | Cumberland County | 25,386 | |
| 12 | Westmoreland County | 22,726 | 13 | Dauphin County | 22,270 | |
| 13 | Dauphin County | 22,270 | 21 | Delaware County | 12,809 | |
| 14 | Fayette County | 20,159 | 32 | Erie County | 1,468 | |
| 15 | Franklin County | 19,638 | 14 | Fayette County | 20,159 | |
| 16 | Allegheny County | 15,087 | 15 | Franklin County | 19,638 | |
| 17 | Mifflin County | 13,609 | 24 | Greene County | 8,605 | |
| 18 | Adams County | 13,172 | 19 | Huntingdon County | 13,008 | |
| 19 | Huntingdon County | 13,008 | 2 | Lancaster County | 43,403 | |
| 20 | Luzerne County | 12,839 | 20 | Luzerne County | 12,839 | |
| 21 | Delaware County | 12,809 | 26 | Lycoming County | 5,414 | |
| 22 | Bedford County | 12,039 | 28 | Mercer County | 3,228 | |
| 23 | Somerset County | 10,188 | 17 | Mifflin County | 13,609 | |
| 24 | Greene County | 8,605 | 11 | Montgomery County | 24,150 | |
| 25 | Beaver County | 5,776 | 5 | Northampton County | 30,062 | |
| 26 | Lycoming County | 5,414 | 7 | Northumberland County | 27,797 | |
| 27 | Butler County | 3,916 | 1 | Philadelphia County | 81,009 | |
| 28 | Mercer County | 3,228 | 23 | Somerset County | 10,188 | |
| 29 | Wayne County | 2,562 | 33 | Venango County | 1,130 | |
| 30 | Armstrong County | 2,399 | 34 | Warren County | 233 | |
| 31 | Crawford County | 2,346 | 6 | Washington County | 28,298 | |
| 32 | Erie County | 1,468 | 29 | Wayne County | 2,562 | |
| 33 | Venango County | 1,130 | 12 | Westmoreland County | 22,726 | |
| 34 | Warren County | 233 | 9 | York County | 25,643 |