The town is named for Henry Marie Brackenridge. The borough once had glass factories. An Allegheny Technologies, Inc. steel mill, Allegheny Ludlum Steel Brackenridge Plant, plays a prominent role in the community. The population stood at 3,421 in 1910 and at 6,400 in 1940. The population was 3,543 at the 2000 census. The drop in the population is attributable to the decline of the steel industry and the consequent loss of employment in the Pittsburgh region.
Brackenridge is located at .
According to the United States Census Bureau, the borough has a total area of , of which, of it is land and of it (7.27%) is water. Its average elevation is above sea level .
As of the census of 2000, there were 3,543 people, 1,507 households, and 931 families residing in the borough. The population density was 6,924.2 people per square mile (2,682.3/km²). There were 1,700 housing units at an average density of 3,322.4/sq mi (1,287.0/km²). The racial makeup of the borough was 95.03% White, 3.44% African American, 0.11% Native American, 0.23% Asian, 0.03% Pacific Islander, 0.37% from other races, and 0.79% from two or more races. Hispanic or Latino of any race were 0.54% of the population.
There were 1,507 households out of which 24.6% had children under the age of 18 living with them, 43.9% were married couples living together, 13.6% had a female householder with no husband present, and 38.2% were non-families. 34.2% of all households were made up of individuals and 17.3% had someone living alone who was 65 years of age or older. The average household size was 2.28 and the average family size was 2.91.
In the borough the population was spread out with 20.5% under the age of 18, 7.2% from 18 to 24, 28.1% from 25 to 44, 22.0% from 45 to 64, and 22.3% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 80.7 males. For every 100 females age 18 and over, there were 78.3 males.
The median income for a household in the borough was $30,050, and the median income for a family was $41,803. Males had a median income of $30,661 versus $21,821 for females. The per capita income for the borough was $19,040. About 6.8% of families and 9.4% of the population were below the poverty line, including 15.9% of those under age 18 and 9.9% of those age 65 or over.