The land that became Lawnside was purchased by Abolitionists for freed and escaped slaves, as well as other African Americans, in 1840.
On April 20, 1926, an "Official Special Election" was held in the Borough of Lawnside. Just one month earlier, on March 24, 1926, Governor of New Jersey A. Harry Moore signed into law New Jersey General Assembly Bill 561, dissolving Centre Township, of which Lawnside was a part, and incorporating the Borough of Lawnside, which also included portions of the borough of Barrington. With its first election, Lawnside became the first independent self-governing African American community north of the Mason-Dixon line.
Lawnside is home to a massive United Parcel Service depot.
As of the census of 2000, there were 2,692 people, 1,026 households, and 700 families residing in the borough. The population density was 1,919.7 people per square mile (742.4/km). There were 1,110 housing units at an average density of 791.6/sq mi (306.1/km). The racial makeup of the borough was 1.75% White, 93.61% African American, 1.00% Native American, 0.52% Asian, 0.07% Pacific Islander, 0.48% from other races, and 2.56% from two or more races. Hispanic or Latino of any race were 2.38% of the population.
There were 1,026 households out of which 23.5% had children under the age of 18 living with them, 40.1% were married couples living together, 22.4% had a female householder with no husband present, and 31.7% were non-families. 28.4% of all households were made up of individuals and 14.6% had someone living alone who was 65 years of age or older. The average household size was 2.62 and the average family size was 3.23.
In the borough the population was spread out with 23.3% under the age of 18, 7.4% from 18 to 24, 22.7% from 25 to 44, 27.8% from 45 to 64, and 18.8% who were 65 years of age or older. The median age was 42 years. For every 100 females there were 83.4 males. For every 100 females age 18 and over, there were 77.4 males.
The median income for a household in the borough was $45,192, and the median income for a family was $55,197. Males had a median income of $34,881 versus $31,331 for females. The per capita income for the borough was $18,831. About 10.3% of families and 10.7% of the population were below the poverty line, including 16.0% of those under age 18 and 12.1% of those age 65 or over.
As part of the 2000 Census, 93.61% of Lawnside's residents identified themselves as being African American. This was the 30th highest percentage of African American people in any place in the United States with 1,000 or more residents identifying their ancestry and the highest in the Northeastern United States.
New Jersey Transit offers bus service to Philadelphia on the 403 route, with local service on the 451.