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,
[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 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.
[12] The Clark Fork is a Class I river for recreational purposes in Montana from Warm Springs Creek to the Idaho border.
[13] The Clark Fork should not be confused with the
Clarks Fork of the Yellowstone River, which is located in Montana and
Wyoming.