The longest rivers of the United States include 38 that have
main stems of at least 500 miles (800 km) long. The main stem is "the primary downstream segment of a river, as contrasted to its tributaries".[1] The
United States Geological Survey (USGS) defines a main-stem segment by listing coordinates for its two end points, called the source and the mouth. Some well-known rivers like the
Atchafalaya,[2]Willamette,[3] and
Susquehanna[4] are not included in this list because their main stems are shorter than 500 miles.
Seven rivers in this list cross or form international boundaries. Two—the
Yukon and
Columbia rivers—begin in Canada and flow into the United States. Three—the
Milk and
Saint Lawrence rivers and the
Red River of the North—begin in the United States and flow into Canada. Of these, only the Milk River crosses the international border twice, leaving and then re-entering the United States.[5] Two rivers, the
Colorado and the
Rio Grande, begin in the United States and flow into or form a border with Mexico.[5] In addition, the
drainage basins of the
Mississippi and
Missouri rivers extend into Canada,[6][7] and the basin of the
Gila River extends into Mexico.[8]
Sources report hydrological quantities with varied precision. Biologist and author
Ruth Patrick, describing a table of
high-discharge U.S. rivers, wrote that data on discharge, drainage area, and length varied widely among authors whose works she consulted. "It seems," she said, "that the wisest course is to regard data tables such as the present one as showing the general ranks of rivers, and not to place too much importance on minor (10–20%) differences in figures."[9]
Table
The primary source for watershed and discharge data in the table below is Rivers of North America. Conflicting data from other sources, if the difference is greater than 10 percent, is reported in the notes. Discharge refers to the flow at the mouth.[n 1] In the "States, provinces, and image" column, the superscripts "s" and "m" indicate "source" and "mouth". Non-U.S. states appear in italics. Except in the "States, provinces, and image" column, abbreviations are as follows: "km" for "kilometer", "mi" for "mile", "s" for "second", "m" for "meter", and "ft" for "foot".
Key
† River is not entirely within the United States.
‡ Watershed is not entirely within the United States.
^Dams, diversions for agriculture, and other human alterations to rivers have greatly affected the discharge of some rivers over time. For example, the virgin discharge of the Colorado River is estimated to have been 20,000 ft3/s (566 m3/s) compared to 1,400 ft3/s (~40 m3/s) in 2005.[10]
^Of the total, 10,700 mi2 (28,000 km2), about two percent of the basin, is in Canada.[6][7]
^Kammerer: 2,340 mi (3,766 km).[16]The Atlas of Canada: 2,348 mi (3,779 km).[6]
^Of the total, 10,700 mi2 (27,800 km2), less than one percent of the basin, is in Canada.[6][7]
^Of this total, 714 mi (1,149 km) are in Canada. This amounts to about 36 percent of the main-stem length.[6]
^The Atlas of Canada also lists the total basin size at 324,000 mi2 (839,200 km2), split between 125,000 mi2 (323,800 km2), about 39 percent, in Canada and 199,000 mi2 (515,400 km2), about 61 percent, in the United States.[6]
^Kammerer: 1,900 mi (3,100 km).[16] University of Texas (UT): 1,799 mi (2,895 km).[24] The river forms the U.S.–Mexico border for 1.251 mi (2,013 km) (about 70 percent of its main-stem length) from
El Paso to the Gulf of Mexico.[24]
^Rivers of North America says that of this total only about 170,000 mi2 (450,000 km2) of the basin contribute water to the river.[26] The University of Texas (UT) says, "The river collects rain, snowmelt and spring water from an area [of] about 215,338 mi2 [557,722 km2] including closed basins."[24] It says that 87,020 mi2 (225,380 km2) of the basin (about 48 percent), not counting
closed basins, are in Mexico, while 93,821 mi2 (242,994 km2) (about 52 percent) are in the United States.[24] Kammerer cites a total basin size of 336,000 mi2 (870,000 km2).[16]
^According to the Utah Division of Water Resources, 75 mi (121 km) of the river are in Mexico. This amounts to about 5 percent of the main-stem length.[27] Of this, 17 mi (27 km) form the border between Mexico and the United States.[28]
^The
United Nations Environment Programme cites a total basin size of 246,000 mi2 (637,000 km2), split between 2,000 mi2 (5,200 km2) (about 1 percent) in Mexico and 244,000 mi2 (632,000 km2) (about 99 percent) in the United States.[28]
^Derived by subtracting the length of the
East Fork Arkansas River of roughly 16 mi (26 km)[31] from Kammerer's total of 1,459 mi (2,348 km).[16]
^About 498 mi (801 km) are in Canada.[6] This amounts to about 40 percent of the main-stem length.
^The Atlas of Canada lists the total watershed at 259,200 mi2 (671,300 km2), split between 39,700 mi2 (102,800 km2) (about 15 percent) in Canada and 219,500 mi2 (568,500 km2) (about 85 percent) in the United States.[6] Kammerer's figure for the total watershed is 265,000 mi2 (690,000 km2).[16]
^Also known as the Dakota River or Jim River and not to be confused with the
James River of Virginia.
^This is the average discharge for the years 1982–94, derived by adding the discharge for each of these years and dividing by 13.
^According to The Canadian Encyclopedia, a 110-mi (170 km) stretch of the river flows through Canada. This amounts to about 18 percent of the main-stem length.[84]
^The Atlas of Canada: 23,600 mi2 (61,200 km2) split between 8,300 mi2 (21,600 km2) (about 35 percent) in Canada and 15,300 mi2 (39,600 km2) (about 65 percent) in the United States.[6]
^According to the
U.S. Army Corps of Engineers, a 115-mi (185 km) stretch of the river forms part of the U.S.–Canada border. This amounts to about 19 percent of the main-stem length.[91]
^Kammerer: 396,000 mi2 (1,030,000 km2).[16]The Atlas of Canada: 519,000 mi2 (1,344,200 km2), of which 324,000 mi2 (839,200 km2) (about 62 percent) is in Canada and 195,000 mi2 (505,000 km2) (about 38 percent) is in the United States.[6]
^The main-stem length is calculated by subtracting the length of the
Nabesna River from Kammerer's total of 659 mi (1,061 km).[16] The Nabesna River is roughly 75 mi (121 km) long, calculated by adding the 60 mi (97 km) from the Nabesna mouth to Camp Creek[101] to the distance, 15 mi (24 km), from Camp Creek to Nabesna Glacier,[102] Kammerer's most remote source for the Tanana.
^This is only a close approximation of the entire basin. It does not include a small fraction of the basin below the river gauge, located about 25 mi (40 km) upstream of the river mouth.
^This is the average discharge for the years 1990–2010, derived by adding the discharge for each of these years and dividing by 21.
^Of the total basin, 53,500 mi2 (138,600 km2) (about 48 percent) are in Canada and 57,500 mi2 (148,900 km2) (about 52 percent) are in the United States.[6]
^
abArias, E.; Albar, M.; Parra, I; Reza, M.
"Regional Definition"(PDF). United Nations Environment Programme. pp. 20–21. Archived from
the original(PDF) on May 31, 2017. Retrieved May 30, 2017.
^"Colorado River". Geographic Names Information System (GNIS). United States Geological Survey. February 8, 1980. Retrieved February 4, 2011.
^Personius, Robert Giles; Eddy, Samuel (February 18, 1955). "Fishes of the Little Missouri River". Copeia. 1955 (1). American Society of Ichthyologists and Herpetologists: 41.
doi:
10.2307/1439450.
^"Little Missouri River". Geographic Names Information System. United States Geological Survey (USGS). February 13, 1980. Retrieved February 23, 2011.
Patrick, Ruth (1995). Rivers of the United States: Volume II: Chemical and Physical Characteristics. New York: John Wiley & Sons. p. 24.
ISBN978-0-471-10752-1.
The longest rivers of the United States include 38 that have
main stems of at least 500 miles (800 km) long. The main stem is "the primary downstream segment of a river, as contrasted to its tributaries".[1] The
United States Geological Survey (USGS) defines a main-stem segment by listing coordinates for its two end points, called the source and the mouth. Some well-known rivers like the
Atchafalaya,[2]Willamette,[3] and
Susquehanna[4] are not included in this list because their main stems are shorter than 500 miles.
Seven rivers in this list cross or form international boundaries. Two—the
Yukon and
Columbia rivers—begin in Canada and flow into the United States. Three—the
Milk and
Saint Lawrence rivers and the
Red River of the North—begin in the United States and flow into Canada. Of these, only the Milk River crosses the international border twice, leaving and then re-entering the United States.[5] Two rivers, the
Colorado and the
Rio Grande, begin in the United States and flow into or form a border with Mexico.[5] In addition, the
drainage basins of the
Mississippi and
Missouri rivers extend into Canada,[6][7] and the basin of the
Gila River extends into Mexico.[8]
Sources report hydrological quantities with varied precision. Biologist and author
Ruth Patrick, describing a table of
high-discharge U.S. rivers, wrote that data on discharge, drainage area, and length varied widely among authors whose works she consulted. "It seems," she said, "that the wisest course is to regard data tables such as the present one as showing the general ranks of rivers, and not to place too much importance on minor (10–20%) differences in figures."[9]
Table
The primary source for watershed and discharge data in the table below is Rivers of North America. Conflicting data from other sources, if the difference is greater than 10 percent, is reported in the notes. Discharge refers to the flow at the mouth.[n 1] In the "States, provinces, and image" column, the superscripts "s" and "m" indicate "source" and "mouth". Non-U.S. states appear in italics. Except in the "States, provinces, and image" column, abbreviations are as follows: "km" for "kilometer", "mi" for "mile", "s" for "second", "m" for "meter", and "ft" for "foot".
Key
† River is not entirely within the United States.
‡ Watershed is not entirely within the United States.
^Dams, diversions for agriculture, and other human alterations to rivers have greatly affected the discharge of some rivers over time. For example, the virgin discharge of the Colorado River is estimated to have been 20,000 ft3/s (566 m3/s) compared to 1,400 ft3/s (~40 m3/s) in 2005.[10]
^Of the total, 10,700 mi2 (28,000 km2), about two percent of the basin, is in Canada.[6][7]
^Kammerer: 2,340 mi (3,766 km).[16]The Atlas of Canada: 2,348 mi (3,779 km).[6]
^Of the total, 10,700 mi2 (27,800 km2), less than one percent of the basin, is in Canada.[6][7]
^Of this total, 714 mi (1,149 km) are in Canada. This amounts to about 36 percent of the main-stem length.[6]
^The Atlas of Canada also lists the total basin size at 324,000 mi2 (839,200 km2), split between 125,000 mi2 (323,800 km2), about 39 percent, in Canada and 199,000 mi2 (515,400 km2), about 61 percent, in the United States.[6]
^Kammerer: 1,900 mi (3,100 km).[16] University of Texas (UT): 1,799 mi (2,895 km).[24] The river forms the U.S.–Mexico border for 1.251 mi (2,013 km) (about 70 percent of its main-stem length) from
El Paso to the Gulf of Mexico.[24]
^Rivers of North America says that of this total only about 170,000 mi2 (450,000 km2) of the basin contribute water to the river.[26] The University of Texas (UT) says, "The river collects rain, snowmelt and spring water from an area [of] about 215,338 mi2 [557,722 km2] including closed basins."[24] It says that 87,020 mi2 (225,380 km2) of the basin (about 48 percent), not counting
closed basins, are in Mexico, while 93,821 mi2 (242,994 km2) (about 52 percent) are in the United States.[24] Kammerer cites a total basin size of 336,000 mi2 (870,000 km2).[16]
^According to the Utah Division of Water Resources, 75 mi (121 km) of the river are in Mexico. This amounts to about 5 percent of the main-stem length.[27] Of this, 17 mi (27 km) form the border between Mexico and the United States.[28]
^The
United Nations Environment Programme cites a total basin size of 246,000 mi2 (637,000 km2), split between 2,000 mi2 (5,200 km2) (about 1 percent) in Mexico and 244,000 mi2 (632,000 km2) (about 99 percent) in the United States.[28]
^Derived by subtracting the length of the
East Fork Arkansas River of roughly 16 mi (26 km)[31] from Kammerer's total of 1,459 mi (2,348 km).[16]
^About 498 mi (801 km) are in Canada.[6] This amounts to about 40 percent of the main-stem length.
^The Atlas of Canada lists the total watershed at 259,200 mi2 (671,300 km2), split between 39,700 mi2 (102,800 km2) (about 15 percent) in Canada and 219,500 mi2 (568,500 km2) (about 85 percent) in the United States.[6] Kammerer's figure for the total watershed is 265,000 mi2 (690,000 km2).[16]
^Also known as the Dakota River or Jim River and not to be confused with the
James River of Virginia.
^This is the average discharge for the years 1982–94, derived by adding the discharge for each of these years and dividing by 13.
^According to The Canadian Encyclopedia, a 110-mi (170 km) stretch of the river flows through Canada. This amounts to about 18 percent of the main-stem length.[84]
^The Atlas of Canada: 23,600 mi2 (61,200 km2) split between 8,300 mi2 (21,600 km2) (about 35 percent) in Canada and 15,300 mi2 (39,600 km2) (about 65 percent) in the United States.[6]
^According to the
U.S. Army Corps of Engineers, a 115-mi (185 km) stretch of the river forms part of the U.S.–Canada border. This amounts to about 19 percent of the main-stem length.[91]
^Kammerer: 396,000 mi2 (1,030,000 km2).[16]The Atlas of Canada: 519,000 mi2 (1,344,200 km2), of which 324,000 mi2 (839,200 km2) (about 62 percent) is in Canada and 195,000 mi2 (505,000 km2) (about 38 percent) is in the United States.[6]
^The main-stem length is calculated by subtracting the length of the
Nabesna River from Kammerer's total of 659 mi (1,061 km).[16] The Nabesna River is roughly 75 mi (121 km) long, calculated by adding the 60 mi (97 km) from the Nabesna mouth to Camp Creek[101] to the distance, 15 mi (24 km), from Camp Creek to Nabesna Glacier,[102] Kammerer's most remote source for the Tanana.
^This is only a close approximation of the entire basin. It does not include a small fraction of the basin below the river gauge, located about 25 mi (40 km) upstream of the river mouth.
^This is the average discharge for the years 1990–2010, derived by adding the discharge for each of these years and dividing by 21.
^Of the total basin, 53,500 mi2 (138,600 km2) (about 48 percent) are in Canada and 57,500 mi2 (148,900 km2) (about 52 percent) are in the United States.[6]
^
abArias, E.; Albar, M.; Parra, I; Reza, M.
"Regional Definition"(PDF). United Nations Environment Programme. pp. 20–21. Archived from
the original(PDF) on May 31, 2017. Retrieved May 30, 2017.
^"Colorado River". Geographic Names Information System (GNIS). United States Geological Survey. February 8, 1980. Retrieved February 4, 2011.
^Personius, Robert Giles; Eddy, Samuel (February 18, 1955). "Fishes of the Little Missouri River". Copeia. 1955 (1). American Society of Ichthyologists and Herpetologists: 41.
doi:
10.2307/1439450.
^"Little Missouri River". Geographic Names Information System. United States Geological Survey (USGS). February 13, 1980. Retrieved February 23, 2011.
Patrick, Ruth (1995). Rivers of the United States: Volume II: Chemical and Physical Characteristics. New York: John Wiley & Sons. p. 24.
ISBN978-0-471-10752-1.