Northumberland County was erected March 21, 1772, from parts of Lancaster, Cumberland, Berks, Bedford and Northampton. On account of Indian purchases now reaching to the western boundaries of the State, the limits of Northumberland reached to the western and northern boundaries of the State. Her territory was so extensive that she has been known as “The Mother of Counties,” and all or parts of thirty of the present counties of Pennsylvania have been taken from the original territory of “Old Mother Northumberland.” February 26, 1773, was erected the County of Westmoreland, whose territory was taken from Bedford County. It then included the entire southwestern section of the State. The next county to be erected was Washington, on March 28, 1781, and its territory was taken from Westmoreland, as was the County of Fayette, formed September 26, 1783. Thus, Westmoreland was considerably reduced in size within ten years from its organization. Franklin County was erected September 9, 1784, and its territory taken from Cumberland. The following day, September 10, 1784, Montgomery County was formed from a part of Philadelphia County, the last territory to be taken from the original county. March 4, 1785, Dauphin was cut off from Lancaster; September 25, 1786, Luzerne was erected from Northumberland, and September 20, 1787, Huntingdon was formed from Bedford. Allegheny County was formed from Westmoreland and Washington Counties, September 24, 1788. Mifflin was formed from Cumberland and Northumberland Counties September 19, 1789. Old Chester County lost part of its territory when Delaware County was cut from it September 26, 1789. Thus the county which comprised the most ancient settlements in Pennsylvania was now formed into the new County of Delaware, and the organization of counties in the southeastern part of the State completed. When the County of Lycoming was cut from Northumberland, April 13, 1795, it was for years the largest county of the State. Four days later the County of Somerset was formed from Bedford. Green County was cut from Washington February 9, 1796, thus completing the formation of counties in the southwest corner of the State. The next county to be formed was that of Wayne, which was set off from Northampton March 21, 1797, and formed the northeastern corner of the State. Adams was erected from York January 22, 1800, and February 13 following Center was formed from parts of Northumberland, Lycoming, Mifflin and Huntingdon, and March 12 eight new counties—Armstrong, Beaver, Butler, Crawford, Erie, Mercer, Venango and Warren—were formed. Thus, the remaining corner of the State was organized. The counties were taken from Lycoming and Allegheny, Westmoreland furnished a part of Armstrong and Washington yielded up a portion for Beaver, but Allegheny furnished the largest amount of territory for the new counties. Indiana was cut from Westmoreland and Lycoming, March 30, 1803.