Pennington was established as a borough by an Act of the New Jersey Legislature on January 31, 1890, from portions of Hopewell Township, based on the results of a referendum held on January 21, 1890.
As of the census of 2000, there were 2,696 people, 1,013 households, and 761 families residing in the borough. The population density was 2,801.0 people per square mile (1,084.3/km²). There were 1,040 housing units at an average density of 1,080.5/sq mi (418.3/km²). The racial makeup of the borough was 94.96% White, 2.63% African American, 1.00% Asian, 0.41% from other races, and 1.00% from two or more races. Hispanic or Latino of any race were 1.19% of the population.
There were 1,013 households out of which 40.8% had children under the age of 18 living with them, 66.2% were married couples living together, 7.1% had a female householder with no husband present, and 24.8% were non-families. 22.0% of all households were made up of individuals and 12.4% 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 3.14.
In the borough the population was spread out with 28.7% under the age of 18, 4.9% from 18 to 24, 23.6% from 25 to 44, 27.9% from 45 to 64, and 15.0% who were 65 years of age or older. The median age was 41 years. For every 100 females there were 92.2 males. For every 100 females age 18 and over, there were 85.0 males.
The median income for a household in the borough was $90,366, and the median income for a family was $107,089. Males had a median income of $84,912 versus $43,068 for females. The per capita income for the borough was $45,843. About 0.7% of families and 2.4% of the population were below the poverty line, including 1.4% of those under age 18 and 4.1% of those age 65 or over.
Route 31 passes through Pennington, providing access to Interstate 95 at Exit 4. Additionally, Exit 3B along I-95 will take you to Scotch Road N, which provides access to all of Hopewell Township, Mercer County, New Jersey.The town is also home to a newly designated NJ Transit bus stop at the corner of South Main Street and West Delaware Avenue.