The expansive Delaware Bay, lined with marshy lowlands, is a busy, important channel for both commercial and recreational vessels. At the inlet from the North Atlantic Ocean the 15 miles separating Cape May, NJ, and Cape Henlopen, DE, begins the Delaware’s role as part of the New Jersey–Delaware state border. It is 782 square miles in area and extends from the ocean for 52 miles to the junction of Delaware River and Alloway Creek to the northwest. Beyond the bay the Delaware River is lined with refineries, shipyards and marine terminals for the 35 miles north to the City of Philadelphia. Delaware Bay feeds 11 rivers, several of which have protected salt water marshes.