Allentown was incorporated as a borough by an Act of the New Jersey Legislature on January 29, 1889, from portions of Upper Freehold Township, based on the results of a referendum held that day.
Allentown's shopping district has antique and specialty shops, as well as restaurants. Many historic homes and historic buildings are located in the borough.
The borough received the 'Village Center' designation in 2002.
As of the census of 2000, there were 1,882 people, 708 households, and 526 families residing in the borough. The population density was 3,097.1 people per square mile (1,191.2/km²). There were 718 housing units at an average density of 1,181.6/sq mi (454.5/km²). The racial makeup of the borough was 90.65% White, 6.43% African American, 0.58% Native American, 0.64% Asian, 0.58% from other races, and 1.12% from two or more races. Hispanic or Latino of any race were 1.91% of the population.
There were 708 households out of which 36.4% had children under the age of 18 living with them, 63.1% were married couples living together, 8.8% had a female householder with no husband present, and 25.6% were non-families. 21.3% of all households were made up of individuals and 5.5% had someone living alone who was 65 years of age or older. The average household size was 2.66 and the average family size was 3.13.
In the borough the population was spread out with 26.7% under the age of 18, 5.2% from 18 to 24, 32.5% from 25 to 44, 25.8% from 45 to 64, and 9.8% who were 65 years of age or older. The median age was 38 years. For every 100 females there were 89.7 males. For every 100 females age 18 and over, there were 89.9 males.
The median income for a household in the borough was $71,193, and the median income for a family was $79,843. Males had a median income of $55,441 versus $38,667 for females. The per capita income for the borough was $29,455. About 1.0% of families and 2.3% of the population were below the poverty line, including 2.6% of those under age 18 and 2.1% of those age 65 or over.
By car, Allentown is about one hour southwest of Manhattan via the New Jersey Turnpike and about 50 minutes northeast of Philadelphia. Both Princeton and Trenton are easily accessible from Allentown.