Blair County was created on February 26, 1846, from parts of Huntingdon and Bedford counties, which had both been formed in the late 1770’s. The region had been home to squatters for years before it was finally purchased in a treaty with the Indians in 1754. The Blair family began to settle in the area after the Revolution. They went on to lead the movement to form the new county, which was ultimately named for the family patriarch, John Blair. The county’s early industries included agriculture and iron mining and smelting; the region became powerful with the expansion of the Pennsylvania Railroad.

The county seat, Hollidaysburg, incorporated as a borough in 1831, became the terminal of the Portage Railroad, which carried canal boats over the mountains to Johnstown. As canals lost their primacy and railroads took over, the PRR built its first small repair shops on the site of the David Robeson farm. The shops became the world’s largest railroad repair yards and ultimately became the town of Altoona. The railroad was the county’s main employer through the 1970’s. Though its mountainous terrain is not always favorable to cultivation, Blair County thrived on the Pennsylvania Railroad, bituminous coal, and lumber and paper production.