For 400 years Maryland and Virginia have disputed control of the Potomac and its North Branch, since both states' original colonial charters grant the entire river rather than half of it as is normally the case with boundary rivers.
In its first state constitution adopted in 1776, Virginia ceded its claim to the entire river but reserved free use of it, an act disputed by Maryland.
Both states acceded to the 1765 Mount Vernon Compact and the 1877 Black-Jenkins Award which granted Maryland the river bank-to-bank from the low water mark on the Virginia side, while permitting Virginia full riparian rights short of obstructing navigation.

From 1957 to 1996, the Maryland Department of the Environment (MDE) routinely issued permits applied for by Virginia entities concerning use of the Potomac.
 However, in 1996 the MDE denied a permit submitted by the Fairfax County Water Authority to build a water intake 725 feet (220 m) offshore, citing potential harm to Maryland's interests by an increase in Virginia sprawl caused by the project.
After years of failed appeals within the Maryland government's appeal processes, in 2000 Virginia took the case to the Supreme Court of the United States, which exercises original jurisdiction in cases between two states.
Maryland claimed Virginia lost its riparian rights by acquiescing to MDE's permit process for 63 years (MDE began its permit process in 1933).
A Special Master appointed by the Supreme Court to investigate recommended the case be settled in favor of Virginia, citing the language in the 1785 Compact and the 1877 Award.
On December 9, 2003, the Court agreed in a 7–2 decision.

The original charters are silent as to which branch from the upper Potomac serves as the boundary, but this was settled by the 1785 Compact.
When West Virginia seceded from Virginia in 1863, the question of West Virginia's succession in title to the lands between the branches of the river was raised, as well as title to the river itself.
Claims by Maryland to West Virginia land north of the South Branch (all of Mineral and Grant Counties and parts of Hampshire, Hardy, Tucker and Pendleton Counties) and by West Virginia to the Potomac's high-water mark were rejected by the Supreme Court in two separate decisions in 1910.
For 400 years Maryland and Virginia have disputed control of the Potomac and its North Branch, since both states' original colonial charters grant the entire river rather than half of it as is normally the case with boundary rivers. In its first state constitution adopted in 1776, Virginia ceded its claim to the entire river but reserved free use of it, an act disputed by Maryland. Both states acceded to the 1765 Mount Vernon Compact and the 1877 Black-Jenkins Award which granted Maryland the river bank-to-bank from the low water mark on the Virginia side, while permitting Virginia full riparian rights short of obstructing navigation.
From 1957 to 1996, the Maryland Department of the Environment (MDE) routinely issued permits applied for by Virginia entities concerning use of the Potomac.  However, in 1996 the MDE denied a permit submitted by the Fairfax County Water Authority to build a water intake 725 feet (220 m) offshore, citing potential harm to Maryland's interests by an increase in Virginia sprawl caused by the project. After years of failed appeals within the Maryland government's appeal processes, in 2000 Virginia took the case to the Supreme Court of the United States, which exercises original jurisdiction in cases between two states. Maryland claimed Virginia lost its riparian rights by acquiescing to MDE's permit process for 63 years (MDE began its permit process in 1933). A Special Master appointed by the Supreme Court to investigate recommended the case be settled in favor of Virginia, citing the language in the 1785 Compact and the 1877 Award. On December 9, 2003, the Court agreed in a 7–2 decision.
The original charters are silent as to which branch from the upper Potomac serves as the boundary, but this was settled by the 1785 Compact. When West Virginia seceded from Virginia in 1863, the question of West Virginia's succession in title to the lands between the branches of the river was raised, as well as title to the river itself. Claims by Maryland to West Virginia land north of the South Branch (all of Mineral and Grant Counties and parts of Hampshire, Hardy, Tucker and Pendleton Counties) and by West Virginia to the Potomac's high-water mark were rejected by the Supreme Court in two separate decisions in 1910.
Potomac River