South River (Raritan River) Wikipedia
The South River is a tributary of the Raritan River in central New Jersey in the United States.
The South River, formed by the confluence of Matchaponix Brook and Manalapan Brook, becomes tidal downstream of the Duhernal Lake dam and joins the Raritan River approximately midway between New Brunswick and Perth Amboy.
The South River has two mouths. It used to loop inefficiently to its confluence with the Raritan River, so a shortcut called Washington Canal was created.
The river lends its name to the borough of South River.