
South Plainfield
- County:
- Middlesex County
- County Seat:
- No
- Area (mi²):
- 8.296
- State:
- New Jersey
South Plainfield borough is located in Middlesex County, New Jersey. South Plainfield borough has a 2025 population of 24,103. South Plainfield borough is currently declining at a rate of -0.06% annually and its population has decreased by -0.75% since the most recent census, which recorded a population of 24,286 in 2020.
The average household income in South Plainfield borough is $143,868 with a poverty rate of 3.55%. The median age in South Plainfield borough is 41.7 years: 39.7 years for males, and 43.1 years for females.