Its official name is Municipality of Norristown, though it was formerly a borough operating under Pennsylvania's Borough Code and is frequently referred to as "the borough" even in statements by its officials. However, since 1986, Norristown has been governed under home rule charters, not under Pennsylvania's Borough Code. The 1986 charter was properly forwarded to the Commonwealth of Pennsylvania for inclusion in the Pennsylvania Code. The succeeding 2004 home rule charter has not been so published, but may be read at the municipal website. Some areas outside the municipality, in the surrounding townships, also have "Norristown, PA" mailing addresses. The entire Municipality of Norristown is within the 19401 ZIP code.
Norristown was incorporated as a borough in 1812, its population then being about 500. It was enlarged in 1853. In 1900, 22,265 people lived here; in 1910, 27,875; in 1920, 32,319; and in 1940, 38,181, making Norristown the most populous borough in Pennsylvania. As of the as of 2004 census, Norristown population was 30,873.
As of the census of 2000, there were 31,282 people, 12,028 households, and 7,144 families residing in the borough. The population density was 8,871.6 people per square mile (3,421.5/km²). There were 13,531 housing units at an average density of 3,837.4/sq mi (1,480.0/km²). The racial makeup was 54.32% White, 34.80% Black or African American, 0.20% Native American, 2.96% Asian, 0.03% Pacific Islander, 4.61% from other races, and 3.07% from two or more races. Hispanic or Latino of any race were 10.49% of the population.
There were 12,028 households out of which 28.7% had children under the age of 18 living with them, 33.7% were married couples living together, 19.8% had a female householder with no husband present, and 40.6% were non-families. 32.7% of all households were made up of individuals and 9.2% had someone living alone who was age 65 or older. The average household size was 2.52 and the average family size was 3.22.
In the borough the population was spread out with 25.1% under the age of 18, 10.5% from 18 to 24, 32.6% from 25 to 44, 20.1% from 45 to 64, and 11.8% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 94.9 males. For every 100 females age 18 and over, there were 92.8 males.
The median income for a household in the borough was $35,714, and the median income for a family was $42,357. Males had a median income of $32,113 versus $26,746 for females. The per capita income for the borough was $17,977. About 13.5% of families and 17.2% of the population were below the poverty line, including 23.6% of those under the age of 18 and 13.8% of those 65 and older.