DELAWARE RIVER, a stream of the Atlantic slope of the United States, meeting tide-water at Trenton (N.J.), 13om. above its mouth. Its total length, from the head of the longest branch to the capes, is 410m., and above the head of the bay its length is 36om. It constitutes in part the boundary between Pennsylvania and New York, the boundary between New Jersey and Pennsylvania, and, for a few miles, the boundary between Delaware and New Jersey. The main or west branch rises in Schoharie county (N.Y.), about 1,886ft. above the sea, and flows tortuously through the plateau in a deep trough until it emerges from the Catskills. Other branches rise in Greene and Delaware counties, New York. In the upper portion of its course the varied scenery of its hilly and wooded banks is ex quisitely beautiful. After leaving the mountains and plateau, the river flows down broad Appalachian valleys, skirts the Kittatinny range, which it crosses at Delaware water-gap, between nearly vertical walls of sandstone, and passes through a quiet and charm ing country of farm and forest, diversified with plateaus and escarpments, until it crosses the Appalachian plain and enters the hills again at Easton (Pa.). From this point it is flanked at intervals by fine hills, and in places by cliffs, of which the finest are the Hockamixon rocks, three miles long and more than 2ooft. high. At Trenton there is a fall of eight feet.
Below Trenton the river becomes a broad, sluggish inlet of the sea, with many marshes along its side, widening steadily into its great estuary, Delaware bay. Its main tributaries in New York are Mongaup and Neversink rivers and Callicoon creek; from Pennsylvania, Lackawaxen, Lehigh and Schuylkill rivers ; and from New Jersey, Rancocas creek and Musconetcong and Maurice rivers. Commerce was once important on the upper river, but only before the beginning of railway competition (1857). Of the various early canals only two are of any importance now; the canal from Trenton to New Brunswick which unites the waters of the Delaware and Raritan rivers and the Delaware and Chesa peake canal which joins the waters of the Delaware with those of Chesapeake bay. The magnitude of the commerce of Philadelphia has made the improvements of the river below that port of great importance. At a cost of many millions of dollars to the U.S. Government a 32ft. channel 600ft. wide has been opened from the deep water in Delaware bay to Philadelphia and a 12f t. channel from there to Trenton.