Historically, manufacturing was Catasauqua's principal industry, and, in 1839, it was the location of the first manufactured anthracite iron in the nation. Catasauqua's population in 1910 was 5,250. The population was 6,588 at the 2000 census. The word Catasauqua is shortened to "Catty" in local dialect when speaking of the place.
As of the census of 2000, there were 6,588 people, 2,616 households, and 1,750 families residing in the borough. The population density was 5,205.7 people per square mile (2,002.9/km²). There were 2,747 housing units at an average density of 2,170.6/sq mi (835.1/km²). The racial makeup of the borough was 95.60% White, 1.18% African American, 0.33% Native American, 0.59% Asian, 0.02% Pacific Islander, 1.08% from other races, and 1.20% from two or more races. Hispanic or Latino of any race were 3.54% of the population.
There were 2,616 households out of which 33.6% had children under the age of 18 living with them, 49.5% were married couples living together, 12.1% had a female householder with no husband present, and 33.1% were non-families. 27.6% of all households were made up of individuals and 10.8% had someone living alone who was 65 years of age or older. The average household size was 2.50 and the average family size was 3.04.
In the borough the population was spread out with 25.0% under the age of 18, 7.7% from 18 to 24, 32.1% from 25 to 44, 22.3% from 45 to 64, and 12.9% who were 65 years of age or older. The median age was 36 years. For every 100 females there were 94.1 males. For every 100 females age 18 and over, there were 91.1 males.
The median income for a household in the borough was $42,432, and the median income for a family was $48,589. Males had a median income of $32,320 versus $45,730 for females. The per capita income for the borough was $18,906. About 5.4% of families and 8.0% of the population were below the poverty line, including 11.7% of those under age 18 and 11.2% of those age 65 or over.