County

Date Erected

Current Area (Square Miles)

Lancaster County

May 10, 1729

21,186

1.

York County

August 19, 1749

909

2.

Cumberland County

January 27, 1750

555

3.

Berks County

March 11, 1752

862

4.

Bedford County

March 9, 1771

1,148

5.

Northumberland County

March 21,1772

453

6.

Westmoreland County

Feb. 26, 1773

1,024

7.

Washington County

March 28, 1781

857

8.

Fayette County

September 26, 1783

802

9.

Franklin County

September 9, 1784

754

10.

Dauphin County

March 4, 1785

518

11.

Huntington County

September 20, 1787

894

12.

Allegheny County

September 24, 1788

728

13.

Mifflin County

September 19, 1789

431

14.

Lycoming County

April 13, 1795

1,216

15.

Somerset County

April 17, 1795

1,085

16.

Greene County

February 9, 1796

578

17.

Adams County

January 22, 1800

526

18.

Centre County

February 13, 1800

1,115

19.

Beaver County

March 12, 1800

440

20.

Indiana County

March 30, 1803

825

21.

Cambria County

March 26, 1804

695

22.

Schuylkill County

March 1, 1811

784

23.

Lebanon County

February 16, 1813

363

24.

Union County

March 22, 1813

318

25.

Perry County

March 22, 1820

551

26.

Juniata County

March 2, 1831

386

27.

Blair County

February 26, 1846

531

28.

Fulton County

April 19, 1850

435

29.

Montour County

May 3, 1850

130

30.

Snyder County

March 2, 1855

327

Lancaster County - today

946

Lancaster County Original Size

21,186