Holliaysburg is a borough in Blair County, Pennsylvania, on the Juniata River, 7 miles (11 km) south of Altoona. It is the county seat of Blair County. It is part of the Altoona, Pennsylvania, Metropolitan Statistical Area and is one of the communities that comprises the Altoona Urban Area. In 1910, 3,734 lived there, and in 1940, 5,910 residents were counted. The population was 5,368 at the 2000 census. On the outskirts of Hollidaysburg are the Ant Hill Woods, famous for their colony of ants. Coal, iron ore, ganister, and limestone are found in the vicinity. In the past, the borough had foundries and machine shops, a silk mill, car works and classification yards. In 1900, 2,998 people lived in the borough.