The PAGenWeb Project

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	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