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.
The center of Hollidaysburg is frequently referred to as "The Diamond," where the buildings and parking spaces form a diamond. This area serves as the hub for parades, festivals and other town celebrations.
As of the census of 2000, there were 5,368 people, 2,224 households, and 1,349 families residing in the borough. The population density was 2,261.0 people per square mile (874.5/km²). There were 2,392 housing units at an average density of 1,007.5/sq mi (389.7/km²). The racial makeup of the borough was 98.19% White, 0.82% African American, 0.17% Native American, 0.26% Asian, 0.06% from other races, and 0.50% from two or more races. Hispanic or Latino of any race were 0.48% of the population.
There were 2,224 households out of which 26.0% had children under the age of 18 living with them, 45.7% were married couples living together, 12.0% had a female householder with no husband present, and 39.3% were non-families. 35.3% of all households were made up of individuals and 16.7% had someone living alone who was 65 years of age or older. The average household size was 2.21 and the average family size was 2.88.
In the borough the population was spread out with 20.5% under the age of 18, 7.9% from 18 to 24, 26.8% from 25 to 44, 23.1% from 45 to 64, and 21.7% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 88.4 males. For every 100 females age 18 and over, there were 86.8 males.
The median income for a household in the borough was $36,758, and the median income for a family was $43,209. Males had a median income of $33,315 versus $24,627 for females. The per capita income for the borough was $20,634. About 5.5% of families and 8.8% of the population were below the poverty line, including 9.9% of those under age 18 and 7.3% of those age 65 or over.