Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Riverside is a hamlet (and census-designated place) in Suffolk County, New York, USA. The population was 2,875 at the 2000 census. Riverside is in the Town of Southampton and derives its name from being on the south bank of the Peconic River.Riverside is located at 40°54′28″N 72°39′45″W / 40.90778°N 72.6625°W / 40.90778; -72.6625 (40.907643, -72.662591).According to the United States Census Bureau, the CDP has a total area of 5.2 square miles (13 km2), of which, 5.1 square miles (13 km2) of it is land and 0.1 square miles (0.26 km2) of it (1.92%) is water.As of the census of 2000, there were 2,875 people, 846 households, and 485 families residing in the CDP. The population density was 563.4 per square mile (217.7/km²).