Instruct: Given a question, retrieve documents that can help answer the question.
Query: What is the longest fork in the American River?
The North Fork is the longest tributary of the American River, at 88 miles (142km).[6] It begins at an elevation of about 7,900 feet (2,400m) near Lake Tahoe in Placer County at Mountain Meadow Lake, just northeast of Granite Chief and immediately due west of Squaw Valley Ski Resort. It flows westward through remote wilderness areas.
The river flows roughly from east to south, with the North Fork Salmon River, Middle Fork Salmon River, South Fork Salmon River, combining to form the Salmon River, which empties into the Queets River. The river's length, including its longest source tributary, the Middle Fork, is . The main stem Salmon River, below the North Fork, is about long. The Salmon's drainage basin is in area.
The Edisto River is one of the longest free-flowing blackwater rivers in North America, flowing over 250 meandering miles from its sources in Saluda and Edgefield counties, to its Atlantic Ocean mouth at Edisto Beach, South Carolina. It rises in two main tributaries (North Fork & South Fork) from springs under the Sandhills region of West Central South Carolina, just to the south of the Piedmont Fall Line. It is the longest and largest river system completely contained by the borders of South Carolina. Its name comes from the Edisto subtribe of the Cusabo Indians.
The East, West, and Middle Forks all originate north of Grays Harbor and flow generally south. The East Fork Hoquiam River is the longest, at long. It joins the West Fork to form the main stem Hoquiam River near Hoquiam and Aberdeen. The West Fork and Middle Fork are both long. The West Fork is paralleled by U.S. Route 101. It joins the East Fork form the main stem Hoquiam River. The Middle Fork is a tributary of the West Fork.
The American River is fed by its North, Middle, and South forks, which are located in El Dorado County, Placer County, and Sacramento County. The river's three forks originate in the Tahoe and Eldorado National Forests.[17] The North and Middle Forks join near Auburn, and continue downstream as the North Fork, although the Middle Fork carries a higher volume of water. The North and South Forks join in Folsom Lake. All three forks are known for their verdant canyons, forested ridges, massive rock formations, trails, backcountry winter adventuring among snowy peaks, fishing and white water rafting. There are various fish species that live within the American River such as Chinook Salmon and Steelhead Trout.[18]
Below the dam, the river bends south, passing under the Foresthill Bridge, the highest bridge in California, then receives the Middle Fork American River, its largest tributary, from the left. The valley widens as the river flows south past Auburn, soon emptying into the north arm of Folsom Lake, a reservoir formed in 1955 by the Folsom Dam. Its waters mingle with that of the South Fork American River to form the American River, a tributary of the Sacramento River.
Three Forks is a city in Gallatin County, Montana, United States and is located within the watershed valley system of both the Missouri and Mississippi rivers drainage basins — and is historically considered the birthplace or start of the Missouri River. The population was 1,869 at the 2010 census. The city of Three Forks is named so because it lies geographically near the point, in nearby Missouri Headwaters State Park, where the Jefferson, Madison, and Gallatin Rivers converge to form the Missouri River — the longest single river in North America, as well as the major portion of the Missouri-Mississippi River System from the headwaters near Three Forks to its discharge into the Gulf of Mexico. Three Forks is part of the Bozeman, MT Micropolitan Statistical Area of approximately 100,000 people and the greater Bozeman demographic area of approximately 125,000 people.
The Middle Fork American River is one of the three main branches of the American River in Northern California. The river flows from its headwaters in the Sierra Nevada, in a generally southwest direction, to join the North Fork American River near Auburn.
The city of American Fork is named after this river.
The description "American" in the river's name is to distinguish it from the Spanish Fork River that also originates in the Wasatch Range; alternatively, it could have been named after the American Fur Company.
The American River is specifically known for its whitewater rafting. The South Fork has Class III rapids, the Middle Fork has Class IV rapids, and the North Fork has Class IV spring run-off rapids.[39] All three rivers also feature Class II sections. The areas with rapids still feature beautiful scenic views and wildlife, which is what makes it the most popular whitewater rafting location in California [39]
West of the divide, the Clark Fork of the Columbia (not to be confused with the Clarks Fork of the Yellowstone River) rises near Butte and flows northwest to Missoula, where it is joined by the Blackfoot River and Bitterroot River. Farther downstream, it is joined by the Flathead River before entering Idaho near Lake Pend Oreille. The Pend Oreille River forms the outflow of Lake Pend Oreille. The Pend Oreille River joined the Columbia River, which flows to the Pacific Ocean—making the long Clark Fork/Pend Oreille (considered a single river system) the longest river in the Rocky Mountains. The Clark Fork discharges the greatest volume of water of any river exiting the state. The Kootenai River in northwest Montana is another major tributary of the Columbia.
The South Fork Flathead River is a major river in Northwestern Montana in the northwest United States. It is one of the three main forks of the Flathead River, a tributary of the Clark Fork River (the Pend Oreille River). The north-northwest trending river is about long, making it the second longest tributary of the Flathead River.
The river begins in the Bob Marshall Wilderness south of Glacier National Park, as does the Middle Fork Flathead River, at the confluence of two streams, Danaher Creek and Youngs Creek, between the Flathead Range and the Swan Range. For some , the river flows freely north-northwest, meandering through a forested and undeveloped valley. The river enters a narrow gorge, running north, then begins to enter the backwater of Hungry Horse Reservoir after receiving Meadow Creek from the left. Hungry Horse Reservoir occupies much of the lower half of the river, covering . The reservoir trends north then northwest, and the river then passes through the arched Hungry Horse Dam, just a few miles above the mouth. After it leaves the dam, the river enters a narrow gorge and, exiting the canyon for the final time, runs northwest past the town of Hungry Horse, then joins the Flathead River, just a few miles below its headwaters at the North Fork and Middle Forks' convergence.
The Skokomish River is a river in Mason County, Washington, United States. It is the largest river flowing into Hood Canal, a western arm of Puget Sound. From its source at the confluence of the North and South Forks the main stem Skokomish River is approximately long. The longer South Fork Skokomish River is , making the length of the whole river via its longest tributary about . The North Fork Skokomish River is approximately long. A significant part of the Skokomish River's watershed is within Olympic National Forest and Olympic National Park.
The river has three forks: the South Fork, Wheatfield Fork and the North Fork. The South Fork is the longest and travels northwest, parallel to the coast along the San Andreas Fault rift zone. The Wheatfield Fork begins west of Lake Sonoma and has the largest flow of the three forks. Its tributaries include Tombs, Wolf, House, Haupt and Fuller creeks. Wheatfield is the first fork to combine with the South Fork. Buckeye Creek, a tributary of the river, joins the South Fork next. It is followed by Rockpile Creek and Big Pepperwod Creek. The North Fork is the only part of the river in Mendocino County. It travels roughly southwest towards the coast along the San Andreas Fault rift zone and meets the South Fork at the border between the counties, a few miles before the river flows into the ocean.
The North Fork American River is the longest branch of the American River in Northern California. It is long from its source at the crest of the Sierra Nevada, near Lake Tahoe, to its mouth at Folsom Lake northeast of Sacramento. Prior to the construction of Folsom Dam the river was about longer making for a total length of .
A number of major Sierra rivers have their origins in the park. The South Fork Kings River flows from near Taboose Pass, on the park's eastern boundary, and drains much of the southern half of the park, carving the canyon from which the park takes its name. The Middle Fork Kings River originates near Mount Powell and drains most of the park's northern half. A smaller section in the northern tip of the park is drained by the South Fork of the San Joaquin River. The Kings River falls more than from the Sierra crest to Pine Flat Reservoir in the San Joaquin Valley – the longest undammed drop of any North American river.
The North Fork and its tributaries provides one of the most biologically diverse habitats in North America. The North Fork features scenic multi-use trails along forested ridgetops and riparian corridors. It flows freely as a designated National Wild and Scenic Rivers System river until reaching the North Fork Dam, which was built to contain mining debris. This dam creates the small Lake Clementine just north of the Foresthill Bridge and upstream of the confluence with the Middle Fork American River at Auburn. Below the confluence, the North Fork continues several miles until reaching Folsom Lake. Both the North Fork and Middle Fork feature archaeological and historic sites of ancient Native American culture and 1850s Gold Rush habitation.
The American River (Río de los Americanos during the period before 1847 ruled by Mexico) is a 120-mile-long river in California that runs from the Sierra Nevada mountain range to its confluence with the Sacramento River in the Sacramento Valley. Via the Sacramento River, it is part of the San Francisco Bay watershed. This river is fed by the melting snowpack of the Sierra Nevada and its many headwaters and tributaries, including the North Fork American River, the Middle Fork American River, and the South Fork American River.
The Middle Fork Satsop River rises in the foothills of the Olympic Mountains and flows south, passing through steep gorges and canyons. At long it is the second longest tributary. Shortly below the Middle Fork's confluence with Baker Creek its valley widens as the river approaches its confluence with the East Fork Satsop River. Most of the watershed of the Middle Fork is second-growth forest used for timber production.
The East Fork (officially known as East Fork Chowchilla River) is the longest of the three forks and is formed by the confluence of several small, unnamed streams on the south side of Chowchilla Mountain, in the Sierra National Forest. It flows roughly south past the locality of Harris Ranch, receiving Oliver Creek and several other small, unnamed tributaries along the way. It converges with the West Fork south of Bailey Flats, and a few miles south of where the Middle and West Forks converge.
The "South Fork Eel River Wilderness" was designated in 2006, stretching along portions of the South Fork Eel and extending westward to the Pacific Ocean. The wilderness area borders that of the King Range Wilderness, which is said to be the "longest stretch of undeveloped coastline in the United States outside of Alaska".
Silver Fork American River is a tributary of the South Fork American River in the Sierra Nevada near Lake Tahoe in Northern California. 
The West Fork Satsop River rises in the southern Olympic Mountains. It flows south through a narrow gorge. In its final miles the river valley broadens. At long, the West Fork is the longest tributary. The total river length from the West Fork's source to the mouth of the main stem Satsop River is approximately . The length from the source of the Canyon River is nearly as long, at . Its watershed is large. Much of the watershed is privately owned timber lands. The West Fork has two major tributaries, the long Canyon River and the long Little River. The Canyon River, West Fork, and Middle Fork all originate close to one another in the Olympic Mountains. The Canyon River's source is approximately east of the source of the West Fork and west of the source of the Middle Fork. These rivers originate in the southern Olympic Mountains in the general vicinity of Chapel Peak, Dusk Point, and Anderson Butte.
The headwaters of the North Fork Skykomish River are located in the Henry M. Jackson Wilderness near Dishpan Gap along the Pacific Crest Trail. It flows as a small stream off the north slope of Skykomish Peak. The Wild Sky Wilderness protects tributaries and forests adjacent to the North Fork Skykomish, although not the river itself. The river flows generally in a southwestern direction from its source to its mouth. Just before picking up Goblin Creek, the river flows through a short but impressive canyon and within that canyon the river drops over Deer Falls. A short ways down from that, the river flows through an even shorter but very twisted and unusually shaped canyon at Bear Creek Falls.The South Fork Skykomish River begins at the confluence of the Tye River and the Foss River, to the east of Skykomish. From the confluence the South Fork flows northwest. Near the eastern boundary of the city of Skykomish, the Beckler River joins it. To the west of the city of Skykomish, the Miller River joins it. Shortly before converging with the North Fork the river drops over Eagle Falls, followed by Canyon Falls and then, finally, Sunset Falls before its confluence with the North Fork.In the 1890s the Great Northern Railway was built along the Skykomish, South Fork Skykomish, and Tye Rivers, crossing the crest of the Cascades at Stevens Pass. Today the track is owned by BNSF Railway, known as the Burlington Northern Railroad from 1970 to 1995. Stevens Pass is named after the Great Northern surveyor John Frank Stevens. Two railroad tunnels, both called Cascade Tunnel, were built at Stevens Pass. The first one was built slightly north of the pass. It was replaced in 1929 with the New Cascade Tunnel, which at long was for nearly 60 years the longest railroad tunnel in North America and is still the longest in the United States. The New Cascade Tunnel is a few miles south of Stevens Pass. Its western entrance is near the confluence of Tunnel Creek and the Tye River. A small amount of the water flows out of both tunnels into the Tye River. An interpretive center for the Iron Goat Trail, located at Scenic on the upper Tye River, describes the history of the area including the old railroad and new trail. The interpretive center was built near the site of one of the greatest railroad tragedies in American history, the Wellington Disaster.
The South Fork Coquille River is the longest tributary of the Coquille River in coastal Oregon in the United States. From its headwaters in the Southern Oregon Coast Range, the river flows northwest to join the North Fork Coquille River at Myrtle Point, forming the main stem Coquille. The South Fork is about long, and its watershed drains roughly of rural Coos County.