Created on February 26, 1846 from parts of Huntingdon and Bedford counties, Blair County was formed and named for the Honorable John Blair, a prominent citizen born at Blair’s Gap (now in Allegheny Township). Blair was the son of captain Thomas Blair, a  native of Scotland, and a soldier in the Revolutionary Army, who after the independence of the colonies  established a home in the Gap, which has since borne his name. The stream that comes through this gap was also called Blair’s Run after he settled there. Whether it had an earlier name is not known. Captain Blair, owned four hundred acres of land, two saw mills, two distilleries, several slaves and considerable other personal property.  He died in 1808. 
Hollidaysburg, the county seat, was incorporated as a borough on August 10, 1836, and named for early settler, Adam and William Holliday.

Before the county’s formation the area was located on the Frankstown Path and was dangerous to settle because of threats from Indians. It was visited by the Catholic priest Prince Demetrius Gallitzin. The Blair family appeared after the Revolution and led the movement to form the county. In 1831 Hollidaysburg became the terminal of the Portage Railroad that carried canal boats over the mountains to Johnstown. Altoona arose because of the Pennsylvania Railroad’s yards founded there in 1846. This was the main employer in the county until the 1970’s.

Iron production diminished after 1865, but Blair had produced much bituminous coal, paper and printing products, as well as the lumber used by the canal and the railroad. It’s mountainous terrain is unfavorable for cultivation, but Blair ranks twenty-fourth among Pennsylvania’s sixty-seven counties in income from livestock. One fourth of the land is held in farms. Originally settled by German and Scotch-Irish groups, Altoona’s railroad employment brought about a much wider ethnic mix

Blair county is made up of one city, Altoona; 9 boroughs to include Bellwood, duncansivill, Hollidasburg, Martinsburg, newry, roaring Spring, Tunnelhill, Tyrone and Williamsburg and includes 15 townships.