Pennsylvania County Formation
County
Date Formed
 County of Origin County Seat
Adams 22 Jan 1800 York Gettysburg
Allegheny 24 Sep 1788 Washington and Westmoreland Pittsburgh
Armstrong 12 Mar 1800 Allegheny, Lycoming, and Westmoreland Kittanning
Beaver 12 Mar 1800 Allegheny and Washington Beaver
Bedford 9 Mar 1771 Cumberland Bedford
Berks 11 Mar 1752 Chester, Lancaster, and Philadelphia Reading
Blair 26 Feb 1846 Bedford and Huntingdon Hollidaysburg
Bradford (Ontario) 21 Feb 1810 Luzerne and Lycoming Towanda
Bucks 1682 Original County Doylestown
Butler 12 Mar 1800 Allegheny Butler
Cambria 26 Mar 1804 Bedford, Huntingdon, and Somerset Ebensburg
Cameron 29 Mar 1860 Clinton, Elk, McKean, and Potter Emporium
Carbon 13 Mar 1843 Monroe and Northampton Jim Thorpe
Centre 13 Feb 1800 Huntingdon, Lycoming, Mifflin, and Northumberland Bellefonte
Chester 1682 Original County West Chester
Clarion 11 Mar 1839 Armstrong and Venango Clarion
Clearfield 26 Mar 1804 Huntingdon and Lycoming Clearfield
Clinton 21 Jun 1839 Centre and Lycoming Lock Haven
Columbia 22 Mar 1813 Northumberland Bloomsburg
Crawford 12 Mar 1800 Allegheny Meadville
Cumberland 27 Jan 1750 Lancaster Carlisle
Dauphin 4 Mar 1785 Lancaster Harrisburg
Delaware 26 Sep 1789 Chester Media
Elk 18 Apr 1843 Clearfield, Jefferson, and McKean Ridgway
Erie 12 Mar 1800 Allegheny and Crawford Erie
Fayette 26 Sep 1783 Westmoreland Uniontown
Forest 11 Apr 1848 Jefferson and Venango Tionesta
Franklin 9 Sep 1784 Cumberland Chambersburg
Fulton 19 Apr 1850 Bedford McConnellsburg
Greene 9 Feb 1796 Washington Waynesburg
Huntingdon 20 Sep 1787 Bedford Huntingdon
Indiana 30 Mar 1803 Lycoming and Westmoreland Indiana
Jefferson 26 Mar 1804 Lycoming Brookville
Juniata 2 Mar 1831 Mifflin Mifflintown
Lackawanna 13 Aug 1878 Luzerne Scranton
Lancaster 10 May 1729 Chester Lancaster
Lawrence 20 Mar 1849 Beaver and Mercer New Castle
Lebanon 16 Feb 1813 Dauphin and Lancaster Lebanon
Lehigh 6 Mar 1812 Northampton Allentown
Luzerne 25 Sep 1786 Northumberland Wilkes-Barre
Lycoming 13 Apr 1795 Northumberland Williamsport
McKean 26 Mar 1804 Lycoming Smethport
Mercer 12 Mar 1800 Allegheny and Crawford Mercer
Mifflin 19 Sep 1789 Cumberland and Northumberland Lewistown
Monroe 1 Apr 1836 Northampton and Pike Stroudsburg
Montgomery 10 Sep 1784 Philadelphia Norristown
Montour 3 May 1850 Columbia Danville
Northampton  11 Mar 1752 Bucks Easton
Northumberland 21 Mar 1772 Bedford, Berks, Cumberland, Lancaster, and Northampton Sunbury
Perry 22 Mar 1820 Cumberland New Bloomfield
Philadelphia 1682 Original County Philadelphia
Pike 26 Mar 1814 Wayne Milford
Potter 26 Mar 1804 Lycoming Coudersport
Schuylkill 1 Mar 1811 Berks and Northampton Pottsville
Snyder 2 Mar 1855 Union Middleburg
Somerset  Notes 17 Apr 1795 Bedford Somerset
Sullivan 15 Mar 1847 Lycoming Laporte
Susquehanna 21 Feb 1810 Luzerne Montrose
Tioga 26 Mar 1804 Lycoming Wellsboro
Union 22 Mar 1813 Northumberland Lewisburg
Venango 12 Mar 1800 Allegheny, Crawford, and Lycoming Franklin
Warren 12 Mar 1800 Allegheny, Crawford, Lycoming, and Venango Warren
Washington 28 Mar 1781 Westmoreland Washington
Wayne 21 Mar 1798 Northampton Honesdale
Westmoreland 26 Feb 1773 Bedford Greensburg
Wyoming 4 Apr 1842 Luzerne Tunkhannock
York 19 Aug 1749 Lancaster York
Page last updated: December 30, 2023
December 30, 2023