Question: Approximately how long is the river on which Waterloo, Montana is located?

Context paragraphs:
Waterloo Public Library (West Branch): The Waterloo Public Library (West Branch) is a historic building located in Waterloo, Iowa, United States.  The public library was established there in 1896.  It operated out of two rented rooms, one on the east side of the Cedar River and other on the west side.  The Carnegie Foundation agreed to grant the community $21,000 to build this building and a similar amount for the east side branch on April 11, 1902.  Waterloo architect J.G. Ralston designed both buildings in the Neoclassical style.  They were both dedicated on February 23, 1906.  The single-story brick structure has a projecting entrance pavilion capped with a triangular pediment that is supported by Ionic columns.  Also noteworthy are the corner piers that feature bands of brick squares set into the stone.  In 1977 voters in Waterloo approved a $3,650,000 bond referendum to renovate the city's 1938 post office and federal building to house the library.  The post office vacated the building in 1979 when it relocated.  The old library building was listed on the National Register of Historic Places in 1983.  It now houses law offices.

Clark Fork River: The Clark Fork, or the Clark Fork of the Columbia River, is a river in the U.S. states of Montana and Idaho, approximately 310 mi long.  The largest river by volume in Montana, it drains an extensive region of the Rocky Mountains in western Montana and northern Idaho in the watershed of the Columbia River.  The river flows northwest through a long valley at the base of the Cabinet Mountains and empties into Lake Pend Oreille in the Idaho Panhandle.  The Pend Oreille River in Idaho, Washington, and British Columbia, Canada which drains the lake to the Columbia in Washington, is sometimes included as part of the Clark Fork, giving it a total length of 479 mi , with a drainage area of 25820 sqmi .  In its upper 20 mi in Montana near Butte, it is known as Silver Bow Creek.  Interstate 90 follows much of the upper course of the river from Butte to northwest of Missoula.  The highest point within the river's watershed is Mount Evans at 10641 ft in Deer Lodge County, Montana along the Continental Divide.

Waterloo, Montana: Waterloo is a one-road town (Waterloo Road) located on the northern edge of Madison County, Montana, United States, on the Jefferson River.  Waterloo is equidistant between Whitehall, Montana and Twin Bridges, Montana.  Abutting the Tobacco Root Mountains, Waterloo has an elevation of 4463 feet .

Cow Creek (Montana): Cow Creek is a tributary of the Missouri River, approximately 35 mi long, in north central Montana in the United States.  Cow Creek rises in the southern foothills of the Bear Paw Mountains in western Blaine County and flows east and then south, joining the Missouri approximately 25 mi northeast of Winifred, Montana—or 22 mi upstream from the Fred Robinson Bridge.  Cow Creek flows down to the Missouri in a canyon that passes through the Missouri Breaks, which are severely eroded badlands that extend out on either side from the Missouri River.  The floor of Cow Creek canyon provided a pathway of travel from the Montana plains north of the river, down to the Missouri – at the mouth of Cow Creek, Cow Island made fording the Missouri easier – a steep but short trail on the south bank of the Missouri opposite Cow Creek completed this route which led from the northern Montana plains to the central and southern Montana plains.  This pathway was used by migrating buffalo/bison and nomadic American Natives for centuries.  During the steamboat era on the Missouri River, when low water prevented riverboats getting up to Fort Benton, the mouth of Cow Creek became a river landing and freighting depot, and it was the start of the Cow Island Trail by which freight was moved on to Fort Benton by going north up Cow Creek and then west.  In 1877 the Nez Perce Indian Tribe, fleeing to Canada, had several skirmishes along Cow Creek including the "Battle of Cow Island", and several days later at a camp on Cow Creek the Nez Perce, thinking themselves now beyond the reach of the U.S. Army, made the fateful decision to slow down, rather than push on for the Canada–US border.  Today, modern highways have by passed Cow Creek, and the buffalo and the nomadic Indian are gone.  Cow Creek is dormant, in one of the most remote spots of the isolated regions of the vast area known as the Montana Missouri Breaks.

Tongue River (Montana): The Tongue River is a tributary of the Yellowstone River, approximately 265 mi (426 km) long, in the U.S. states of Wyoming and Montana.  The Tongue rises in Wyoming in the Big Horn Mountains, flows through northern Wyoming and southeastern Montana and empties into the Yellowstone River at Miles City, Montana.  Most of the course of the river is through the beautiful and varied landscapes of eastern Montana, including the Tongue River Canyon, the Tongue River breaks, the pine hills of southern Montana, and the buttes and grasslands that were formerly the home of vast migratory herds of American bison.  The Tongue River watershed encompasses parts of the Cheyenne and Crow Reservations.  The Headwaters lie on the Big Horn National Forest, and the watershed encompasses the Ashland Ranger District of the Custer National Forest.

York Road, Lambeth: York Road is a road in Lambeth, London, running between Westminster Bridge Road (south) and Waterloo Road (north).  To the west is the old County Hall, Shell Centre, Jubilee Gardens and, beyond, the London Eye and the River Thames.  Waterloo station is located on the road's eastern edge, as well as the former Waterloo International Eurostar terminal and General Lying-In Hospital.  The London IMAX cinema is located within the Bullring roundabout at the northern end of the road, on a site previously occupied by Cardboard City for the homeless.

Waterloo Village, New Jersey: Waterloo Village is a restored 19th-century canal town in Byram Township, Sussex County (west of Stanhope) in northwestern New Jersey, United States.  The community was approximately the half-way point in the roughly 102-mile (165 km) trip along the Morris Canal, which ran from Jersey City (across the Hudson River from Manhattan, New York) to Phillipsburg, New Jersey, (across the Delaware River from Easton, Pennsylvania).  Waterloo possessed all the accommodations necessary to service the needs of a canal operation, including an inn, a general store, a church, a blacksmith shop (to service the mules on the canal), and a watermill.  For canal workers, Waterloo's geographic location would have been conducive to being an overnight stopover point on the two-day trip between Phillipsburg and Jersey City.

Waterloo Public Library-East Side Branch: The Waterloo Public Library-East Side Branch is a historic building located in Waterloo, Iowa, United States.  The public library was established here in 1896.  It operated out of two rented rooms, one on the east side of the Cedar River and other on the west side.  The Carnegie Foundation offered a grant of $30,000 to build a new library, but disagreements erupted over whether to place the building on the east side or west side of the river.  They then agreed to grant $40,000 for a mid-river building, or the same amount for two buildings.  In the end they agreed to grant the community $24,000 to build this building and a similar amount for the west side branch.  Waterloo architect John G. Ralston designed both buildings in the Neoclassical style.  Both were dedicated on February 23, 1906.  The single-story Bedford stone structure was built over a raised basement.  It is one of the few stone buildings in Waterloo.  The building has a central portico with paired Ionic columns.  It is part of a larger central mass that is oriented from front to back and sits across the lower hipped roof.

Gardner River: The Gardner River (also known as the Gardiner River) is a tributary of the Yellowstone River, approximately 25 mi long, in northwestern Wyoming and south central Montana in the United States.  The entire river is located within Yellowstone National Park.  It rises on the slope of Joseph Peak, Gallatin Range in the northwestern part of the park, and winds southeast through Gardner's Hole, a broad subalpine basin which is a popular trout fishing location.  Angling on the Gardner is governed by Yellowstone National Park fishing regulations.  After merging with Panther Creek, Indian Creek and Obsidian Creek, it then turns north and flows through a steep canyon where it cuts through a basaltic flow from approximately 500,000 years ago known as Sheepeater Cliffs. Below Sheepeater, Glen Creek out of Golden Gate Canyon and Lava Creek out of Lava Creek Canyon join the Gardner near Mammoth Hot Springs.  The river crosses the 45th parallel in Gardner Canyon and is also home to a popular hot spring known as "The Boiling River".  The river continues north through Gardner Canyon and empties into the Yellowstone near Gardiner, Montana.

Jefferson River: The Jefferson River is a tributary of the Missouri River, approximately 83 mi long, in the U.S. state of Montana.  The Jefferson River and the Madison River form the official beginning of the Missouri at Missouri Headwaters State Park near Three Forks.  It is joined 0.6 mi downstream (northeast) by the Gallatin.

Supporting paragraphs: Waterloo, Montana Jefferson River
Answer: 83 mi