Bladensburg Dueling Grounds is a small spit of land, a fraction of its original size, along Dueling Creek, formerly in the town of Bladensburg, Maryland, and now within the town of Colmar Manor, just to the northeast of Washington, D.C., United States. Dueling Creek, formerly known as '"Blood Run" and "The Dark and Bloody Grounds", is a tributary of the Anacostia River, which was formerly, called the East Branch Potomac River. Following the Civil War, dueling fell out of favor as a means of settling personal grievances and declined rapidly; the last known duel was fought here in 1868.