Hollidaysburg 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 1900, 2,998 people lived in the borough, in 1910, 3,734 lived there, and in 1940, 5,910 residents were counted. The population was 5,791 at the 2010 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.
From 1834 to 1854, the borough was an important port on Pennsylvania Main Line Canal, where the Juniata Division Canal connected to the Allegheny Portage Railroad.
The famous toy known as the Slinky is manufactured within Hollidaysburg by Poof-Slinky, Inc. (formerly James Industries, Inc.). More than a quarter billion Slinkys have been manufactured in the toy's history.