The Anacostia River is a river in the Mid Atlantic region of the United States. It flows from Prince George's County in Maryland into Washington, D.C., where it joins with the Washington Channel and ultimately empties into the Potomac River at Buzzard Point. It is about 8.7 miles long. The name "Anacostia" derives from the area's early history as Nacotchtan…The Anacostia River is a river in the Mid Atlantic region of the United States. It flows from Prince George's County in Maryland into Washington, D.C., where it joins with the Washington Channel and ultimately empties into the Potomac River at Buzzard Point. It is about 8.7 miles long. The name "Anacostia" derives from the area's early history as Nacotchtank, a settlement of Necostan or Anacostan Native Americans on the banks of the Anacostia River.