Potomac River

• 1. Introduction

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  The Potomac River runs 405 miles through one of the most contested and celebrated stretches of American land. It begins in two separate streams high in the mountains of West Virginia and Virginia, threads past coal towns and Civil War battlefields, slides under the windows of the nation's capital, and widens to 11 miles across before merging with the Chesapeake Bay. More than 6 million people live within its watershed today. But those numbers say nothing about what it felt like to stand on its banks in the summer of the 1960s, when President Lyndon Johnson looked at the green algal blooms choking the surface and called it a national disgrace. Nor do they explain why, for four centuries, two states fought in court over who actually owns it. The Potomac is a river that has never belonged to just one story. It has been a borderline, a battlefield, a sewer, a sanctuary, and a political symbol all at once. What shaped it? Who controlled it? And how did a river declared a disgrace earn a grade of B in the 21st century?

• 2. A River With Two Birthplaces

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  At the Fairfax Stone, a boundary marker sitting at the junction of Grant, Tucker, and Preston counties in West Virginia, the North Branch of the Potomac begins. From that single stone, the North Branch travels 27 miles before reaching Jennings Randolph Lake, a man-made reservoir built for flood control. It then cuts a serpentine path northeast through the Allegheny Mountains, passing Bloomington, Luke, and Westernport before reaching Keyser and eventually Cumberland, Maryland. The South Branch tells a different story. Its source lies northwest of Hightown, Virginia, along U.S. Route 250 on the eastern flank of Lantz Mountain, which rises 3,934 feet. From there it follows a narrow valley northeast, passing through the 20-mile-long Smoke Hole Canyon between Big Mountain and Cave Mountain, a stretch that is today habitat for bald eagles. The two branches converge just east of Green Spring in Hampshire County, West Virginia, to form the main stem of the Potomac. From that confluence, the river must still cross five separate geological provinces before it reaches the sea: the Appalachian Plateau, the Ridge and Valley, the Blue Ridge, the Piedmont Plateau, and the Atlantic coastal plain. The point where the Piedmont drops to the coastal plain, at the fall line near Little Falls, is where tides begin to reach the river and salinity starts climbing with every mile downstream.

• 3. The Nation's River

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  Captain John Smith paddled the Potomac in 1608 and made drawings that were later compiled into a map published in London in 1612. He recorded the local Algonquian name as Patawomeck, a word that appears on his map. Native Americans above Great Falls called the river Cohongarooton, meaning honking geese, while below the falls it was Patawomke, meaning river of swans. The name passed through many spellings over the decades, from Patomake to Patowmack and others, before the Board on Geographic Names settled the question officially in 1931, ruling in favor of Potomac. Before European contact, the region was governed by the Algonquian Piscataway confederacy and their allies, led by the Tayac with local chiefs known as Werowances managing individual communities. The confederacy fractured precontact as power shifted south to the Powhatan confederacy. George Washington, who was born, surveyed, and spent most of his adult life within the Potomac basin, proposed the Patowmack Canal to link the Tidewater region near Georgetown with Cumberland, Maryland. Construction began in 1785 and the canal was not completed until 1802; financial troubles forced its closure in 1830. The Chesapeake and Ohio Canal, which ran along the Maryland bank, took over that freight role from 1831 to 1924. Congress placed the capital on the river's banks by act of the 16th of July, 1790. The river so thoroughly defined the nation's identity in that era that, when the Civil War divided the country, the Union's largest army took the river's name: the Army of the Potomac.

• 4. War Along the Banks

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  In 1859, the siege of Harpers Ferry at the river's confluence with the Shenandoah served as a prelude to the Civil War battles that would sweep through the Potomac valley. The 1861 Battle of Ball's Bluff and the 1862 Battle of Shepherdstown were among the clashes fought in and around the river and its tributaries. General Robert E. Lee crossed the Potomac twice to carry the war into the North. The first campaign climaxed at Antietam on the 17th of September, 1862. The second ended at Gettysburg between the 1st and the 3rd of July, 1863. Confederate General Jubal Early crossed the river again in July 1864 during his attempted raid on Washington, D.C. The river itself functioned as the boundary between the Union and the Confederacy throughout the war. It was not a neutral line. Crossing it meant invasion. Every Union commander in the Eastern Theater understood that losing control of the Potomac meant losing the capital. Washington, D.C. began drawing its drinking water from the river with the opening of the Washington Aqueduct in 1864, during the war itself, using an intake constructed at Great Falls.

• 5. Four Centuries of Legal Contest

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  Maryland and Virginia have disputed ownership of the Potomac for roughly 400 years. The source of the conflict is simple: both states' original colonial charters granted each of them the entire river, rather than the usual arrangement where boundary rivers are split down the middle. Virginia's first state constitution, adopted in 1776, ceded Virginia's claim to the full river but reserved free use of it, a concession Maryland disputed. Both states signed the 1785 Mount Vernon Compact and accepted the 1877 Black-Jenkins Award, which gave Maryland the river bank-to-bank from the low-water mark on the Virginia side while preserving Virginia's full right to use the river short of blocking navigation. From 1957 to 1996, Maryland's Department of the Environment routinely issued permits to Virginia entities for Potomac use. In 1996 that changed: Maryland denied a Fairfax County Water Authority permit to build a water intake 725 feet offshore, citing harm to Maryland's interests. Virginia appealed through Maryland's own processes and failed, then took the case to the Supreme Court of the United States in 2000. Maryland argued Virginia had lost its riparian rights by accepting Maryland's permit process for 63 years. The Court's Special Master disagreed and recommended ruling in Virginia's favor; on the 9th of December, 2003, the Court agreed in a 7-2 decision. A separate set of claims arose when West Virginia seceded from Virginia in 1863, raising questions about who inherited Virginia's river titles. The Supreme Court rejected both Maryland's claim to West Virginia land north of the South Branch and West Virginia's claim to the Potomac's high-water mark in two decisions issued in 1910.

• 6. Disgrace and Recovery

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  Throughout the 19th century, mining and agriculture upstream and urban sewage downstream degraded the Potomac steadily. President Abraham Lincoln is said to have escaped to the highlands on summer nights to avoid the river's stench. By the 1960s, dense green algal blooms covered the surface. President Lyndon Johnson declared the river a national disgrace and launched a long-term effort to reduce sewage pollution. One significant project at the time was the expansion of the Blue Plains Advanced Wastewater Treatment Plant, which serves Washington and surrounding communities. The 1972 Clean Water Act drove the construction or expansion of additional sewage treatment plants across the watershed. In the 1980s, controls on phosphorus, one of the principal drivers of eutrophication, were put in place through sewage plant upgrades and restrictions on phosphorus in detergents. By the end of the 20th century, the massive algal blooms had vanished and recreational fishing and boating had returned. In 2007, the Potomac Conservancy graded the river D-plus, citing high pollution levels and reports of intersex fish, a condition linked to endocrine disruption that federal scientists began tracking in 2005. Since 2018 the group has issued the river a grade of B. In March 2019, the Potomac Riverkeeper Network launched a laboratory boat called the Sea Dog to monitor water quality and report results to the public weekly. That same month, a striped bass estimated to weigh 35 pounds was caught near Fletcher's Boat House, treated as a marker of continuing recovery. On the 19th of January, 2026, a large sewage pipe called the Potomac Interceptor ruptured near Lock 10 of the C&O Canal, spilling 300 million gallons into the river, with contamination levels thousands of times higher than what is considered safe for human use.

• 7. Wildlife Past and Present

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  Early European colonists along the Potomac encountered bison, elk, gray wolves, red wolves, and cougars in the dense forests bordering the river. By the middle of the 19th century, all of them had been hunted to extirpation. Beavers and otters followed. Small populations of American mink and American martens survived into the 20th century in isolated areas. There is no record of colonial-era settlers seeing marine mammals in the river, but during the 19th century several sightings of Atlantic bottlenose dolphins were reported. In July 1844, a pod of 14 adults and young was tracked upriver by men in boats as far as the Aqueduct Bridge, roughly the same location as Key Bridge today. Since 2015, likely driven by warmer temperatures, rising water levels in the Chesapeake Bay, and improving water quality, unprecedented numbers of bottlenose dolphins have returned. According to Dr. Janet Mann of Georgetown University's Potomac-Chesapeake Dolphin Project, more than 500 individual members of the species have been identified in the river during that period. The northern snakehead, an invasive fish resembling the native bowfin, was first observed in the Potomac in 2004. The American shad, depressed for many decades, has been rebounding through the ICPRB's American Shad Restoration Project, which began in 1995 and has stocked the river with more than 22 million shad fry, along with constructing a fishway to help adult fish pass around the Little Falls Dam on their way to spawning grounds upstream. All navigable parts of the Potomac were designated a National Recreation Trail in 2006, and in 2019 NOAA established an 18-square-mile section of the river in Charles County, Maryland, as the Mallows Bay-Potomac River National Marine Sanctuary.