The Delaware River is a river on the Atlantic coast of the United States.
It meets tide-water at Trenton, New Jersey. Its total length, from the head of the longest branch to the capes, is 410 miles (660 km), and above the head of the bay its length is 360 miles (579 km).
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. William Penn delegated defense responsibilities of predominately Quaker Pennsylvania to Delaware by setting the New Jersey border to the mean low tide line on the Jersey side of the river.
