The history of Armstrong County, as a municipal unit, began with Section VIII of the Pennsylvania Legislative Act passed on March 12, 1800.  Section VIII provided for the creation of a separate county from the counties of Allegheny, Lycoming, and Westmoreland, which shall be included within the boundaries described therein and henceforth be called Armstrong County.  In its original configuration, the county’s eastern, western, and southern borders were as they exist today; however, its northern lands extended to all land south of the Clarion River, then known as Toby’s Creek.

Section VIII also indicated that the place of holding courts of justice in and for said county shall be fixed on the Allegheny River, at any place at a distance not greater than five miles from the Old Kittanning town.  This established the location of the county seat which later became the town of Kittanning.  The Borough of Kittanning was incorporated on April 2, 1821.

Section XIV of the Act passed on March 12, 1800, provided for the appointment of John Craig, James Sloan, and James Barr as Trustees for the County of Armstrong.

Armstrong County took its name from Colonel John Armstrong, who led a group of 300 Cumberland County militiamen in the destruction of the Delaware Indian village at Kittanning along the Allegheny River.

Below are noted some important historical dates and facts related to the county’s early history:

• 1756 – Delaware Indian Village at Kittanning destroyed by Colonel John Armstrong and his militiamen from Cumberland County
• 1779 – Fort Armstrong built near Manorville
• 1800 – County created from portions of Allegheny, Lycoming and Westmoreland Counties by Legislative Act
• 1802 – Two Presbyterian congregations organized and constructed log churches along the west side of the Allegheny River in then Buffalo Township
• 1803 – Kittanning established as the seat of county government
• 1806 – Saint Patrick’s Roman Catholic Church, oldest Catholic church in Western Pennsylvania, erected in Sugar Creek Township
• 1810 – ‘The Western Eagle’, the first newspaper in Kittanning, published by Captain James Alexander