Assuming we're talking about Maryland of America: The Potomac River. This river separates Maryland from Virginia; five million folk live in it's watershed (including all of DC). read more
List of rivers in Maryland ().. The list is arranged by drainage basin from east to west, with respective tributaries indented under each larger stream's name and ordered from downstream to upstream. read more
Many rivers are tributaries to the Chesapeake Bay, but the three largest are the Potomac, the Patapsco, and the Patuxent. The Potomac River runs west and creates a natural border between Maryland and Virginia, while the Patapsco runs north from the Bay through Baltimore. read more