What is now South Bound Brook was originally formed as a town within Franklin Township. On March 16, 1869, the name of the community was changed to Bloomington, which lasted until May 29, 1891, when the name reverted back to South Bound Brook town. South Bound Brook was incorporated as an independent borough by an Act of the New Jersey Legislature on April 11, 1907, based on the results of a referendum held on May 1, 1907.
As of the census of 2000, there were 4,492 people, 1,632 households, and 1,103 families residing in the borough. The population density was 5,765.3 people per square mile (2,223.6/km²). There were 1,676 housing units at an average density of 2,151.1/sq mi (829.6/km²). The racial makeup of the borough was 78.01% White, 7.77% African American, 0.27% Native American, 4.10% Asian, 0.04% Pacific Islander, 6.57% from other races, and 3.25% from two or more races. Hispanic or Latino of any race were 22.89% of the population.
There were 1,632 households out of which 31.3% had children under the age of 18 living with them, 51.0% were married couples living together, 10.8% had a female householder with no husband present, and 32.4% were non-families. 25.1% of all households were made up of individuals and 8.0% had someone living alone who was 65 years of age or older. The average household size was 2.75 and the average family size was 3.31.
In the borough the population was spread out with 23.5% under the age of 18, 8.8% from 18 to 24, 36.2% from 25 to 44, 21.1% from 45 to 64, and 10.5% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 105.2 males. For every 100 females age 18 and over, there were 100.4 males.
The median income for a household in the borough was $48,984, and the median income for a family was $58,214. Males had a median income of $36,955 versus $30,082 for females. The per capita income for the borough was $21,131. About 3.6% of families and 6.7% of the population were below the poverty line, including 5.5% of those under age 18 and 10.1% of those age 65 or over.
Interstate 287, which provides access and connections to large parts of New Jersey and New York is located very near the western boundary of South Bound Brook and provides two local interchanges.
New Jersey Transit provides frequent train service on the Raritan Valley Line to/from Newark and New York via the nearby Bound Brook Train Station, which is about a five to ten minute walk from downtown South Bound Brook.
NJ Transit bus service to the Port Authority Bus Terminal in Midtown Manhattan is provided on the 114 and 117 routes, with service to Newark available on the 65 bus line.