| Clark Fork | |
| Name Other: | Original name given by Lewis and Clark expedition: Clark's River |
| Map: | Clark Fork Map.png |
| Map Size: | 300 |
| Pushpin Map Size: | 300 |
| Subdivision Type1: | Country |
| Subdivision Name1: | United States |
| Subdivision Type2: | State |
| Subdivision Name2: | Montana, Idaho |
| Subdivision Type5: | Cities |
| Subdivision Name5: | Butte, Missoula |
| Length: | 310miles[1] |
| Discharge1 Location: | Whitehorse Rapids near Cabinet, ID[2] |
| Discharge1 Min: | 762cuft/s |
| Discharge1 Avg: | 21930cuft/s[3] |
| Discharge1 Max: | 195000cuft/s |
| Source1: | Silver Bow Creek |
| Source1 Location: | Butte, Silver Bow County, Montana |
| Source1 Coordinates: | 46.0756°N -112.4656°W[4] |
| Source1 Elevation: | 6882feet[5] |
| Source2: | Warm Springs Creek (Montana) |
| Source2 Location: | Flint Creek Range, Granite County, Montana |
| Source2 Coordinates: | 46.2608°N -113.1367°W[6] |
| Source2 Elevation: | 7466feet[7] |
| Source Confluence Location: | Deer Lodge County, Montana |
| Source Confluence Coordinates: | 46.1867°N -112.7717°W |
| Source Confluence Elevation: | 4795feet[8] |
| Mouth: | Lake Pend Oreille |
| Mouth Location: | Bonner County, Idaho |
| Mouth Coordinates: | 48.1833°N -116.2692°W |
| Mouth Elevation: | 2064feet[9] |
| Basin Size: | 22905sqmi[10] |
| Tributaries Left: | Bitterroot River |
| Tributaries Right: | Blackfoot River, Flathead River, Bull 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 long. The largest river by volume in Montana,[11] 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, with a drainage area of . In its upper 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 in Deer Lodge County, Montana along the Continental Divide.[12]
The Clark Fork is a Class I river for recreational purposes in Montana from Warm Springs Creek to the Idaho border.[13]
It rises as Silver Bow Creek[4] in southwestern Montana, less than from the Continental Divide near downtown Butte, from the confluence of Basin and Blacktail creeks. It flows northwest and north through a valley in the mountains, passing east of Anaconda, where it changes its name to the Clark Fork at the confluence with Warm Springs Creek, then northwest to Deer Lodge. Near Deer Lodge it receives the Little Blackfoot River. From Deer Lodge it flows generally northwest across western Montana, passing south of the Garnet Range toward Missoula. Five miles east of Missoula, the river receives the Blackfoot River.
Northwest of Missoula, the river continues through a long valley along the northeast flank of the Bitterroot Range, through the Lolo National Forest. It receives the Bitterroot River from the south-southwest approximately west of downtown Missoula. Along the Cabinet Mountains, the river receives the Flathead River from the east near Paradise. It receives the Thompson River from the north near Thompson Falls in southern Sanders County.
There are three dams on the lower Clark Fork River. At Thompson Falls, about 100miles northwest of Missoula, the Thompson Falls Dam, actually a series of four dams that bridge between islands in the river, was built atop the falls in 1915. Next, at Noxon, Montana, along the Cabinet Mountains and the northern end of the Bitterroots near the Idaho border, the river is impounded by the Noxon Rapids Dam, completed in 1959 and forming a 20adj=midNaNadj=mid reservoir. It crosses into eastern Bonner County in north Idaho between the towns of Heron, Montana and the town of Cabinet, Idaho. In Idaho, just before the town of Cabinet, the Clark Fork River is dammed again at the Cabinet Gorge Dam. The Cabinet Gorge Dam was completed in the early 1950s, and its reservoir extends eastwards into Montana.
After passing the Cabinet Gorge Dam, the river enters the northeastern end of Lake Pend Oreille, approximately west of the Idaho–Montana border, near the town of Clark Fork, Idaho.
During the last ice age, from approximately 20,000 years ago, the Clark Fork Valley lay along the southern edge of the Cordilleran Ice Sheet covering western North America. The encroachment of the ice sheet formed an ice dam on the river, creating Glacial Lake Missoula, which stretched through the Clark Fork Valley across central Montana. The periodic rupturing and rebuilding of the ice dam released the Missoula Floods, a series of catastrophic floods down the Clark Fork and Pend Oreille into the Columbia, which sculpted many of the geographic features of eastern Washington and the Willamette Valley of Oregon.
In the 19th century, the Clark Fork Valley was inhabited by the Flathead tribe of Native Americans. It was explored by Meriwether Lewis of the Lewis and Clark Expedition during the 1806 return trip from the Pacific. The river is named for William Clark.[14] A middle segment of the river in Montana was formerly known as the Missoula River. The river was also referred to as the Deer Lodge River by Granville Stuart.
In 1809, David Thompson of the North West Company explored the region and founded several fur trading posts, including Kullyspell House at the mouth of the Clark Fork, and Saleesh House on the river near the present-day site of Thompson Falls, Montana. Thompson used the name Saleesh River for the entire Flathead-Clark Fork-Pend Oreille river system.[15] For most of the first half of the 19th century the Clark Fork river and surrounding region was controlled by the British-Canadian North West Company and Hudson's Bay Company.
In the mid-19th century, the Clark Fork River wound through the valley where cattle had replaced bison. This was when Conrad Kohrs purchased a ranch from Johnny Grant that is now called the Grant-Kohrs Ranch,[16] a National Historic Site and Federal Park. For a history of the river and the people, see Grant-Kohrs family and history of Clark Fork River region.
The Clark Fork and the Blackfoot River experienced a record flood in 1908.[17]
Since the late 19th century many areas in the watershed of the river have been extensively mined for minerals, resulting in an ongoing stream pollution problem. Most pollution has come from the copper mines in Butte and the smelter in Anaconda. Many of the most polluted areas have been designated as Superfund sites. Nevertheless, the river and its tributaries are among the most popular destinations for fly fishing in the United States.
Today, the Clark Fork watershed encompasses the largest Superfund site in America. As a mega-site, it includes three major sites: Butte, Anaconda, and Milltown Dam/Clark Fork River's Milltown Reservoir Superfund Site. Each of these major sites is split up into numerous sub-sites known as Operable Units.
Milltown Dam was removed in 2008 at the junction of the Clark Fork and Blackfoot Rivers. Stimson Dam (an old log crib dam) was removed in 2007 just upstream of the Milltown Dam on the Blackfoot River. Stimson Dam was normally under water due to the Milltown Dam. The area that used to be under Milltown Lake has recently become a State Park. Continued remediation and/or restoration of these sites is ongoing.[18]