Delaware Bay is a major estuary

Estuary

An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea....

 outlet of the Delaware River

Delaware River

The Delaware River is a major river on the Atlantic coast of the United States.A Dutch expedition led by Henry Hudson in 1609 first mapped the river. The river was christened the South River in the New Netherland colony that followed, in contrast to the North River, as the Hudson River was then...

 on the Northeast seaboard of the United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 whose fresh water mixes for many miles with the waters of the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

. It is 782 square miles (2,025.4 km²) in area. The bay is bordered by the State of New Jersey

New Jersey

New Jersey is a state in the Northeastern and Middle Atlantic regions of the United States. , its population was 8,791,894. It is bordered on the north and east by the state of New York, on the southeast and south by the Atlantic Ocean, on the west by Pennsylvania and on the southwest by Delaware...

 and the State of Delaware

Delaware

Delaware is a U.S. state located on the Atlantic Coast in the Mid-Atlantic region of the United States. It is bordered to the south and west by Maryland, and to the north by Pennsylvania...

. It was the first site classified in the Western Hemisphere Shorebird Reserve Network

Western Hemisphere Shorebird Reserve Network

The Western Hemisphere Shorebird Reserve Network is a conservation strategy targeting shorebirds in the Americas launched in 1985. Its aim is to protect the nesting, breeding and staging habitats of migratory shorebirds...

.

The pair of Delaware Capes that denote the outermost boundary of the Bay with the Atlantic are Cape Henlopen

Cape Henlopen

Cape Henlopen is the southern cape of the Delaware Bay along the Atlantic coast of the United States. It lies in the state of Delaware, near the town of Lewes, Delaware...

 and Cape May

Cape May

Cape May is a peninsula and island ; the southern tip of the island is the southernmost point of the state of New Jersey, United States. It runs southwards from the New Jersey mainland, separating Delaware Bay from the Atlantic Ocean...

.