The Chesapeake Bay ( ) is an estuary lying inland from the Atlantic Ocean, and surrounded by the North American mainland to the West, and the Delmarva Peninsula to the east. It is the largest such body in the contiguous US. The northern bay is within Maryland, the southern portion within Virginia, and is a very important feature for the ecology and economy of those two states, as well as others. More than 150 major rivers and streams flow into the bay's  drainage basin, which covers parts of six states (New York, Pennsylvania, Delaware, Maryland, Virginia and West Virginia) plus all of the District of Columbia.