Armstrong County is a county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 68,941. The county seat is Kittanning. The county was organized on March 12, 1800, from parts of Allegheny, Westmoreland and Lycoming Counties. It was named in honor of John Armstrong, who represented Pennsylvania in the Continental Congress and served as a major general during the Revolutionary War. Armstrong County is included in the Pittsburgh, PA Metropolitan Statistical Area.

Clearfield County is a sixth-class county located in the U.S. state of Pennsylvania. As of the 2010 census, the population was 81,642. The county seat is Clearfield, and the largest city is DuBois. The county was created in 1804 and later organized in 1822.Clearfield County comprises the DuBois, PA Micropolitan Statistical Area, which is also included in the State College-DuBois, PA Combined Statistical Area.

Indiana County is a county located in the West central part of the U.S. state of Pennsylvania. As of the 2010 census, the population was 88,880. Its county seat is Indiana. Indiana County comprises the Indiana, PA Micropolitan Statistical Area, which is also included in the Pittsburgh-New Castle-Weirton, PA-WV-OH Combined Statistical Area. Prior to the American Revolutionary War, some settlers proposed this as part of a larger, separate colony to be known as Vandalia, but opposing interests and the war intervened. Afterward, claims to the territory by both the states of Virginia and Pennsylvania had to be reconciled. After this land was assigned to Pennsylvania by the federal government according to the placement of the Mason–Dixon line, Indiana County was created on March 30, 1803, from parts of Westmoreland and Clearfield counties and was formally organized in 1806.

Butler County is a county in the western part of the U.S. state of Pennsylvania. As of the 2010 census, the population was 183,862. Its county seat is Butler. Butler County was created on March 12, 1800, from part of Allegheny County and named in honor of General Richard Butler, a hero of the American Revolution. Butler County is part of the Pittsburgh, PA Metropolitan Statistical Area.