largest stream lying wholly within New Jersey, U.S., formed by the confluence of the North Branch Raritan and the South Branch Raritan rivers in western Somerset county. It flows about 75 miles (120 km) generally southeast past Somerville, Bound Brook, and New Brunswick into Raritan Bay of the Atlantic Ocean. Navigable to New Brunswick, it supplies (via pumping) the Spruce Run (1963) and Round Valley (1965) reservoirs. The name was probably derived from an Algonquian word meaning “stream overflows,” or “forked river.”