What is now South Orange was part of a territory purchased from the Lenape Native Americans in 1666 by Robert Treat, who founded Newark that year on the banks of the Passaic River. The unsettled areas north and west of Newark were at first referred to as the uplands. South Orange was called the Chestnut Hills for a time.

There are two claimants to the first English settlement in present-day South Orange. In 1677 brothers Joseph and Thomas Brown began clearing land for a farm in the area northwest of the junction of two old trails that are now South Orange Avenue and Ridgewood Road. A survey made in 1686 states, "note this Land hath a House on it it, built by Joseph Brown and Thomas Brown, either of them having an equal share of it" located at the present southwest corner of Tillou Road and Ridgewood Road.

As of the censusGR2 of 2000, there were 16,964 people, 5,522 households, and 3,766 families residing in the township. The population density was 2,298.2/km² (5,945.3/mi²). There were 5,671 housing units at an average density of 768.3/km² (1,987.5/mi²). The racial makeup of the township was 60.41% White, 31.30% African American, 0.09% Native American, 3.89% Asian, 0.03% Pacific Islander, 1.57% from other races, and 2.71% from two or more races. Hispanic or Latino of any race were 4.93% of the population.

In the village the population was spread out with 22.3% under the age of 18, 17.5% from 18 to 24, 26.1% from 25 to 44, 22.2% from 45 to 64, and 11.9% who were 65 years of age or older. The median age was 35 years. For every 100 females there were 92.3 males. For every 100 females age 18 and over, there were 88.1 males.

The median income for a household in the township was $83,611, and the median income for a family was $107,641. Males had a median income of $61,809 versus $42,238 for females. The per capita income for the township was $41,035. About 1.9% of families and 5.3% of the population were below the poverty line, including 2.6% of those under age 18 and 5.4% of those age 65 or over.