Delaware River (Indian Name Matcerisut-Tori), a river of the United States, formed by two small streams called the Oquago, or Co-quago, and the Popacton, which rise on the western declivity of the Catskill mountains, in Delaware co., N. Y., and unite on the boundary line between New York and Pennsylvania, near the N. E. angle of the latter. Flowing S. E., it separates those states for about 70 m., until it reaches Kittatinny (or Shawangunk) mountain, near Port Jervis, N. Y. At this place it makes a sharp turn to the S. W., and forms the dividing line between New Jersey and Pennsylvania. At the N. extremity of Northampton co., Pa., it passes through a defile formed by perpendicular rocks on either side 1,000 or 1,200 ft. high, known as the Delaware Water Gap. A few miles below Easton it turns again to the S. E., and after passing Trenton meets tide water 132 m. from the sea. The stream, turning again to the S. W., now becomes much wider, and acquires sufficient depth for the passage of steamboats. Philadelphia, on the right bank, is the head of navigation for the largest ships. On the other side of the river, in New Jersey, are the towns of Burlington and Camden, the latter being just opposite Philadelphia. The channel is here about 1 m. wide, and.divided by a small island.

A number of other islands, none of them of great extent, occur in various parts of the stream. Bridges span it at Trenton and several other points. About 40 m. below Philadelphia the river discharges itself into Delaware bay, after a total course of 300 m. In the lower part it separates New Jersey from Delaware. Its chief tributaries are the Lehigh and Schuylkill in Pennsylvania. The Delaware drains about 11,000 sq. m. of territory. The Delaware and Hudson and the Morris canals connect the stream with the Hudson. The Erie railway runs in the valley of the Delaware for a distance of nearly 90 m. The shad fisheries in the lower part of the river are very profitable.