Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. The lake measured about 7,770 square kilometres (3,000 sq mi) and contained about 2,100 cubic kilometres (500 cu mi) of water, half the volume of Lake Michigan.
The Yellowstone River is a tributary of the Missouri River, approximately 692 miles (1,114 km) long, in the Western United States. Considered the principal tributary of upper Missouri, via its tributaries, it drains an area stretching from the Rocky Mountains in the vicinity of Yellowstone National Park, across the mountains and high plains of southern Montana and northern Wyoming.
The Flathead Indian Reservation, located in western Montana on the Flathead River, is home to the Bitterroot Salish, Kootenai, and Pend d'Oreilles tribes – also known as the Confederated Salish and Kootenai Tribes of the Flathead Nation. The reservation was created through the July 16, 1855, Treaty of Hellgate.
The Beaverhead River is an approximately 69-mile-long (111 km) tributary of the Jefferson River in southwest Montana. It drains an area of roughly 4,778 square miles (12,370 km2). The river's original headwaters, formed by the confluence of the Red Rock River and Horse Prairie Creek, are now flooded under Clark Canyon Reservoir, which also floods the first 6 miles (9.7 km) of the river. The Beaverhead then flows through a broad valley northward to join the Big Hole River and form the Jefferson River. With the Red Rock River included in its length, the river stretches another 70 miles (110 km), for a total length of 139 miles (224 km), one of the more significant drainages of south-western Montana.
The Madison River is a headwater tributary of the Missouri River, approximately 183 miles (295 km) long, in Wyoming and Montana. Its confluence with the Jefferson and Gallatin rivers near Three Forks, Montana forms the Missouri River.
The Gallatin River is a tributary of the Missouri River, approximately 120 mi, in the U.S. states of Wyoming and Montana. It is one of three rivers, along with the Jefferson and Madison, that converge near Three Forks, Montana, to form the Missouri.
The Sun River is a tributary of the Missouri River in the Great Plains, approximately 130 mi (209 km) long, in Montana in the United States.
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 miles (500 km) 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 miles (771 km), with a drainage area of 25,820 square miles (66,900 km2). In its upper 20 miles (32 km) 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 Saint Regis. The highest point within the river's watershed is Mount Evans at 10,641 feet (3,243 m) in Deer Lodge County, Montana along the Continental Divide.
The Pend Oreille River is a tributary of the Columbia River, approximately 130 miles (209 km) long, in northern Idaho and northeastern Washington in the United States, as well as southeastern British Columbia in Canada. In its passage through British Columbia its name is spelled Pend-d'Oreille River. It drains a scenic area of the Rocky Mountains along the U.S.-Canada border on the east side of the Columbia. The river is sometimes defined as the lower part of the Clark Fork, which rises in western Montana. The river drains an area of 66,800 square kilometres (25,792 sq mi), mostly through the Clark Fork and its tributaries in western Montana and including a portion of the Flathead River in southeastern British Columbia. The full drainage basin of the river and its tributaries accounts for 43% of the entire Columbia River Basin above the confluence with the Columbia. The total area of the Pend Oreille basin is just under 10% of the entire 258,000-square-mile (670,000 km2) Columbia Basin. Box Canyon Dam is currently underway on a multimillion-dollar project for a fish ladder.
The Confederated Salish and Kootenai Tribes of the Flathead Reservation are a federally recognized tribe in the U.S. state of Montana. The government includes members of several Bitterroot Salish, Kootenai and Pend d'Oreilles tribes and is centered on the Flathead Indian Reservation.
The Flathead River, in the northwestern part of the U.S. state of Montana, originates in the Canadian Rockies to the north of Glacier National Park and flows southwest into Flathead Lake, then after a journey of 158 miles (254 km), empties into the Clark Fork. The river is part of the Columbia River drainage basin, as the Clark Fork is a tributary of the Pend Oreille River, a Columbia River tributary. With a drainage basin extending over 8,795 square miles (22,780 km2) and an average discharge of 11,380 cubic feet per second (322 m3/s), the Flathead is the largest tributary of the Clark Fork and constitutes over half of its flow.
The Bitterroot Valley is located in southwestern Montana, along the Bitterroot River between the Bitterroot Range and Sapphire Mountains, in the Northwestern United States.
The Bitterroot River is a northward flowing 84-mile (135 km) river running through the Bitterroot Valley, from the confluence of its West and East forks near Conner in southern Ravalli County to its confluence with the Clark Fork River near Missoula in Missoula County, in western Montana. The Clark Fork River is tributary to the Columbia River and ultimately, the Pacific Ocean. The Bitterroot River is a Blue Ribbon trout fishery with a healthy population of native westslope cutthroat trout and bull trout. It is the third most fly fished river in Montana behind the Madison and Big Horn Rivers.
The Blackfoot River, sometimes called the Big Blackfoot River to distinguish it from the Little Blackfoot River, is a snow-fed and spring-fed river in western Montana. The Blackfoot River begins in Lewis and Clark County at the Continental Divide, 10 miles (16 km) northeast of the town of Lincoln. The river's headwaters are between Rogers Pass to the north and Stemple Pass to the south. It flows westward through the town of Milltown and enters the Clark Fork River approximately five miles (8 km) east of the city of Missoula.
The Yaak River is a tributary of the Kootenai River in Montana.
The Fisher River is a tributary of the Kootenay River in the U.S. state of Montana. The Fisher River properly begins at the confluence of its two main tributaries, the Pleasant Valley Fisher River and the Silver Butte Fisher River. Of the two tributaries, the Pleasant Valley Fisher River is the larger and is sometimes considered part of the Fisher River proper. A variant name of the Fisher River is Pleasant Valley River, and a variant name of the Pleasant Valley Fisher River is Fisher River.
The Clearwater River is in the northwestern United States, in north central Idaho. Its length is 74.8 miles (120.4 km), it flows westward from the Bitterroot Mountains along the Idaho-Montana border, and joins the Snake River at Lewiston. In October 1805, the Lewis and Clark Expedition descended the Clearwater River in dugout canoes, putting in at "Canoe Camp," five miles (8 km) downstream from Orofino; they reached the Columbia Bar and the Pacific Ocean about six weeks later.
Lewis and Clark Pass is a mountain pass on the continental divide in Montana, United States, at an elevation of 6,424 feet (1,958 m) above sea level. The pass lies at the head of the drainages of the west-flowing Blackfoot River and the east-flowing Dearborn River, in the Helena National Forest in Lewis and Clark County. The Continental Divide Trail traverses north and south through the pass.
