The city's population peaked in the 1930s. Since then, it has declined by two-thirds to just over 9,000 people, from a high of 27,116 in the 1930 census.
2020 census As of the
2020 census, Aliquippa had a population of 9,238 and a median age of 42.3 years. 20.8% of residents were under the age of 18 and 20.6% were 65 years of age or older. For every 100 females there were 86.7 males, and for every 100 females age 18 and over there were 85.0 males age 18 and over. There were 4,250 households in Aliquippa, of which 24.2% had children under the age of 18 living in them. Of all households, 24.8% were married-couple households, 26.3% were households with a male householder and no spouse or partner present, and 41.6% were households with a female householder and no spouse or partner present. About 40.7% of all households were made up of individuals and 16.4% had someone living alone who was 65 years of age or older.
2000 census As of the
2000 census, there were 11,734 people, 5,124 households, and 3,176 families residing in the city. The population density was . There were 5,843 housing units at an average density of . The racial makeup was 62.59% White, 35.52% African American, 0.07% Native American, 0.18% Asian, 0.03% Pacific Islander, 0.18% from other races, and 1.43% from two or more races. Hispanic or Latino of any race were 1.00% of the population. There were 5,124 households, out of which 24.4% had children under the age of 18 living with them, 35.7% were married couples living together, 21.6% had a female householder with no husband present, and 38.0% were non-families. Of all households 35.0% were made up of individuals, and 17.1% had someone living alone who was 65 years of age or older. The average household size was 2.27 and the average family size was 2.92. In the city, the population was spread out, with 23.5% under the age of 18, 7.6% from 18 to 24, 25.5% from 25 to 44, 20.9% from 45 to 64, and 22.5% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 82.7 males. For every 100 females age 18 and over, there were 77.2 males. The median income for a household in the city was $25,113, and the median income for a family was $34,003. Males had a median income of $27,954 versus $21,358 for females. The
per capita income for the city was $13,718. About 17.7% of families and 21.7% of the population were below the
poverty line, including 36.3% of those under age 18 and 10.9% of those age 65 or over. ==Education==