Potomac River

Potomac River
Great Falls of the Potomac River - NPS.jpg
The Potomac River watershed covers the District of Columbia and parts of four states
Native namePatawomeck
CountryUnited States
StateWest Virginia, Maryland, Virginia, District of Columbia
CitiesCumberland, MD, Harpers Ferry, WV, Washington, D.C., Alexandria, VA
Physical characteristics
SourceFairfax Stone
 ⁃ locationPreston County, West Virginia, United States
 ⁃ coordinates39°11′43″N 79°29′28″W / 39°11′43″N 79°29′28″W / 39.19528; -79.49111
 ⁃ elevation3,060 ft (930 m)
MouthChesapeake Bay
 ⁃ location
St. Mary's County, Maryland/Northumberland County, Virginia, United States
 ⁃ coordinates
37°59′57″N 76°14′59″W / 37°59′57″N 76°14′59″W / 37.99917; -76.2497223,760 cu ft/s (673 m3/s) (1996)
 ⁃ locationPoint of Rocks, Maryland
 ⁃ average9,504 cu ft/s (269.1 m3/s)
 ⁃ locationHancock, Maryland
 ⁃ average4,168 cu ft/s (118.0 m3/s)
 ⁃ locationPaw Paw, West Virginia
 ⁃ average3,376 cu ft/s (95.6 m3/s)
Basin features
 ⁃ leftConococheague Creek, Antietam Creek, Monocacy River, Rock Creek, Anacostia River
 ⁃ rightCacapon River, Shenandoah River, Goose Creek, Occoquan River, Wicomico River
Note: Since 1996, the Potomac has been the 'sister river' of the Ara River of Tokyo, Japan[3]

The Potomac River (k/ (About this soundlisten)) is found within the Mid-Atlantic region of the United States and flows from the Potomac Highlands into the Chesapeake Bay. The river (main stem and North Branch) is approximately 405 miles (652 km) long,[4] with a drainage area of about 14,700 square miles (38,000 km2).[5] In terms of area, this makes the Potomac River the fourth largest river along the Atlantic coast of the United States and the 21st largest in the United States. Over 5 million people live within the Potomac watershed.

The river forms part of the borders between Maryland and Washington, D.C., on the left descending bank and West Virginia and Virginia on the river's right descending bank. The majority of the lower Potomac River is part of Maryland. Exceptions include a small tidal portion within the District of Columbia, and the border with Virginia being delineated from "point to point" (thus various bays and shoreline indentations lie in Virginia). Except for a small portion of its headwaters in West Virginia, the North Branch Potomac River is considered part of Maryland to the low water mark on the opposite bank. The South Branch Potomac River lies completely within the state of West Virginia except for its headwaters, which lie in Virginia.


The Potomac River in Washington, D.C., with Arlington Memorial Bridge in the foreground and Rosslyn, Arlington, Virginia in the background

The Potomac River runs 405 miles (652 km) from Fairfax Stone Historical Monument State Park in West Virginia on the Allegheny Plateau to Point Lookout, Maryland, and drains 14,679 square miles (38,020 km2). The length of the river from the junction of its North and South Branches to Point Lookout is 302 miles (486 km).[4] The average daily flow during the water years 1931–2018 was 11,498 cubic feet (325.6 m3) /s.[2] The highest average daily flow ever recorded on the Potomac at Little Falls, Maryland (near Washington, D.C.), was in March 1936 when it reached 426,000 cubic feet (12,100 m3) /s.[2] The lowest average daily flow ever recorded at the same location was 601.0 cubic feet (17.02 m3) /s in September 1966.[2] The highest crest of the Potomac ever registered at Little Falls was 28.10 ft, on March 19, 1936;[6][7] however, the most damaging flood to affect Washington, DC and its metropolitan area was that of October 1942.[8]

Map showing the five geological provinces through which the Potomac River flows [9]
Major sub-basins and cities of the Potomac River basin[10]

The river has two sources. The source of the North Branch is at the Fairfax Stone located at the junction of Grant, Tucker, and Preston counties in West Virginia. The source of the South Branch is located near Hightown in northern Highland County, Virginia. The river's two branches converge just east of Green Spring in Hampshire County, West Virginia, to form the Potomac. As it flows from its headwaters down to the Chesapeake Bay, the Potomac traverses five geological provinces: the Appalachian Plateau, the Ridge and Valley, the Blue Ridge, the Piedmont Plateau, and the Atlantic coastal plain.

Once the Potomac drops from the Piedmont to the Coastal Plain at the Atlantic Seaboard fall line at Little Falls, tides further influence the river as it passes through Washington, D.C. and beyond. Salinity in the Potomac River Estuary increases thereafter with distance downstream. The estuary also widens, reaching 11 statute miles (17 km) wide at its mouth, between Point Lookout, Maryland, and Smith Point, Virginia, before flowing into the Chesapeake Bay.

Other Languages
العربية: نهر بوتوماك
azərbaycanca: Potomak çayı
башҡортса: Потомак
беларуская: Патомак
български: Потомак
brezhoneg: Potomac
català: Riu Potomac
Чӑвашла: Потомак
čeština: Potomac
Deutsch: Potomac River
eesti: Potomac
español: Río Potomac
français: Potomac
galego: Río Potomac
한국어: 포토맥강
հայերեն: Պոտոմակ
Ido: Potomac
Bahasa Indonesia: Sungai Potomac
italiano: Potomac (fiume)
עברית: פוטומק
kernowek: Potomac
Kiswahili: Mto Potomac
Кыргызча: Потомак
latviešu: Potomaka
lietuvių: Potomakas
Nederlands: Potomac (rivier)
occitan: Potomac
polski: Potomak
português: Rio Potomac
română: Râul Potomac
русский: Потомак
Simple English: Potomac River
slovenščina: Potomac (reka)
српски / srpski: Потомак (река)
srpskohrvatski / српскохрватски: Potomac (rijeka)
suomi: Potomac
svenska: Potomac
Türkçe: Potomac Nehri
українська: Потомак
Tiếng Việt: Sông Potomac