conowingo dam
Conowingo Dam credit: U.S. Geological Survey/photo by Wendy S McPherson

At the head of the Chesapeake Bay Watershed is the Susquehanna River. Flowing more than 400 miles, it is the longest Atlantic U.S. river and one of North America’s largest rivers.

The river drains 27,500 square miles, including parts of Pennsylvania, New York and Maryland.

The Susquehanna originates in upstate New York as the North Branch. The West Branch, which begins in western Pennsylvania, coverges with the North Branch near Northumberland, Pa.

Below the Coniwingo Dam near the Susquehanna Flats, the Chesapeake widens into a tidal bay.

Related Information

Chesapeake Bay Watershed