Location: Maryland, Virginia, Pennsylvania, West Virginia, Washington D.C.
The Potomac is the "nation's river," rich in culture and history and the lifeblood of our nation’s capital. The river provides drinking water to more than five million people and offers abundant opportunities for recreation. However, the Potomac is threatened by agricultural and urban pollution that will only get worse if Congress rolls back national clean water protections.
http://www.americanrivers.org/our-work/protecting-rivers/endangered-rivers/2012endangered-potomac.html