Potomac Shores, Inc. v. River Riders, Inc., 98 A.3d 1048

Potomac Shores sues River Riders and River & Trail alleging trespass on land along the Potomac's southerly bank near Potomac Wayside.
Dispute centers on whether the Potomac boundary between Maryland and Virginia shifts with shoreline changes or remains fixed as of a historical date.
1877 Black-Jenkins Award described the boundary as the south bank low-water mark but did not fix a precise location for all segments; it recognized Virginia's rights to the low-water mark on the south shore.
1927 Mathews-Nelson Survey and 1929 monuments attempted to express the Award's boundary; they did not locate or fix the low-water mark for the upper river.
1958 Potomac River Compact reaffirmed riparian rights and referenced the Mathews-Nelson boundary for the tidal portions; the Court treats the non-tidal boundary as shifting.
Circuit Court dismissed for lack of subject matter jurisdiction, concluding Potomac Wayside lies in Virginia; Maryland and Virginia Attorneys General filed amici briefs; the Maryland Court of Special Appeals affirms.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Is the Potomac boundary a shifting or fixed line in the non-tidal portion?	Potomac Shores: fixed boundary as of 1877 or 1927.	Boundary follows shifting shoreline per Black-Jenkins and Whiting guidance.	Boundary is shifting on non-tidal Potomac.
Where is Potomac Wayside land located for purposes of jurisdiction?	Potomac Shores owns land landward of low-water mark on Maryland side.	South bank land at Potomac Wayside lies in Virginia; Maryland lacks jurisdiction.	Potomac Wayside land is in Virginia; circuit court lacked Maryland jurisdiction.
Did Mathews-Nelson or monuments fix the boundary for the upper river?	These instruments fixed the boundary as of their respective dates.	They did not fix the low-water mark or alter the boundary; they express the Award and did not resolve non-tidal reaches.	Neither fixed the boundary; boundary remains shifting.

Morris v. United States, 174 U.S. 196 (U.S. (1899)) (charter grants include Potomac; boundary fixed by low-water mark in later cases)
Maryland v. West Virginia, 217 U.S. 1 (U.S. (1910)) (boundary at low-water mark on the south bank; discusses fixed vs. shifting boundary)
Virginia v. Maryland, 540 U.S. 56 (U.S. (2003)) (recent articulation of riparian rights and boundary location; notes lack of fixed-date resolution)
Illinois v. Kentucky, 500 U.S. 380 (U.S. (1991)) (shoreline boundaries; shifting vs fixed boundary considerations along rivers)
Ohio v. Kentucky, 444 U.S. 335 (U.S. (1980)) (boundary follows river shoreline; historical context informs shift/fix rulings)