The Thompson River is a tributary

Tributary

A tributary or affluent is a stream or river that flows into a main stem river or a lake. A tributary does not flow directly into a sea or ocean...

 of the Clark Fork

Clark Fork (river)

The Clark Fork is a river in the U.S. states of Montana and Idaho, approximately 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, flowing northwest through a long...

 in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Montana

Montana

Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

. It is part of the Columbia River

Columbia River

The Columbia River is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia, Canada, flows northwest and then south into the U.S. state of Washington, then turns west to form most of the border between Washington and the state...

 basin, as Clark Fork is a tributary of the Pend Oreille River

Pend Oreille River

The Pend Oreille River is a tributary of the Columbia River, approximately 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...

, which is a tributary of the Columbia River.

The Thompson River is named in honor of David Thompson

David Thompson (explorer)

David Thompson was an English-Canadian fur trader, surveyor, and map-maker, known to some native peoples as "Koo-Koo-Sint" or "the Stargazer"...

.

Course

The Thompson River originates in Upper Thompson Lake and flows generally south to join Clark Fork near the town of Thompson Falls

Thompson Falls, Montana

Thompson Falls is a city in and the county seat of Sanders County, Montana, United States. The population was 1,321 at the 2000 census.-History:...

.