Interior Northwest

Interior Northwest
Name	Interior Northwest
Settlement type	Region
Subdivision type	Countries
Subdivision name	United States, Canada
Subdivision type1	States/Provinces
Subdivision name1	Idaho, Montana, Washington (state), Oregon, British Columbia

Contents

Interior Northwest is a transboundary region in the northwestern part of North America encompassing inland portions of the Columbia Plateau, the Rocky Mountains, and adjacent basins. The area includes major river systems such as the Columbia River, the Snake River, and tributaries that link to the Pacific Ocean via the Columbia River Gorge. Key population centers include Spokane, Washington, Boise, Idaho, Missoula, Montana, and Kelowna, British Columbia.

Geography

The region covers parts of Idaho Panhandle, the Palouse, the Bitterroot Valley, and the Okanagan Valley, bounded by the Cascade Range, the Selkirk Mountains, and the Canadian Rockies. Significant physiographic features include the Columbia River Basalt Group, the Channeled Scablands, and the Bitterroot Range. Major watersheds are defined by the Columbia River Treaty-era reservoirs such as Lake Roosevelt (Washington) and Lake Koocanusa, and by dams including Grand Coulee Dam, Bonneville Dam, and Duncan Dam.

Indigenous presence predates European contact, with nations including the Nez Perce Tribe, the Coeur d'Alene Tribe, the Salish peoples, and the Okanagan Nation Alliance maintaining seasonal rounds tied to salmon runs and camas prairies. European exploration involved figures associated with Lewis and Clark Expedition and later fur trade networks run by the North West Company and Hudson's Bay Company. The region's 19th-century settlement was shaped by events such as the Oregon Treaty (1846), the Treaty of 1818, and the Idaho Gold Rush, while 20th-century development included projects led by the U.S. Bureau of Reclamation and wartime industries connected to Hanford Site and Spokane's manufacturing.

Climates range from semi-arid steppe in the Palouse to continental alpine in the Cabinet Mountains Wilderness, influenced by rain shadow effects from the Cascade Range. Ecoregions include portions of the Columbia Plateau (ecoregion), Northern Rockies coniferous forests, and Okanagan dry forests. Key species include Columbia River salmon, grizzly bear, gray wolf, elk, bighorn sheep, and endemic plants of the Interior Douglas-fir zone. Conservation efforts involve entities like The Nature Conservancy, British Columbia Ministry of Environment, and U.S. Fish and Wildlife Service.

Population centers such as Spokane County, Washington, Ada County, Idaho, and Missoula County, Montana anchor regional demographics. Indigenous band governments include Coeur d'Alene Tribe of Indians and Kootenai Tribe of Idaho. Economic sectors include agriculture on the Palouse and Okanagan fruit orchards, timber from Inland Northwest forests, mining in the Silver Valley (Idaho), energy from hydroelectricity projects at Priest Rapids Dam and Dworshak Dam, and technology and healthcare hubs in Boise State University-adjacent clusters. Cross-border trade is influenced by policies of United States–Canada relations and agreements such as the North American Free Trade Agreement.

The region is served by corridors including Interstate 90 (I-90), Interstate 84 (I-84), U.S. Route 2, and rail lines operated historically by Northern Pacific Railway and Great Northern Railway, and currently by BNSF Railway and Union Pacific Railroad. Major airports include Spokane International Airport, Boise Airport (Gowen Field), and Kelowna International Airport. Water resource infrastructure comprises irrigation projects from the Bureau of Reclamation and hydroelectric dams under operators such as Bonneville Power Administration and Columbia Basin Project.

Cultural institutions include the Northwest Museum of Arts and Culture, the Boise Art Museum, and performing arts organizations like the Spokane Symphony. Festivals and events feature the Salmon Days festival, Spokane Hoopfest, and the Sun Valley Film Festival connections. Recreation centers on river-based activities on the Columbia River, skiing at Schweitzer Mountain Resort, hiking in Glacier National Park (U.S.) adjacent zones, and viticulture in the Okanagan Valley wine region. Indigenous cultural heritage is promoted by institutions such as the Confederated Salish and Kootenai Tribes cultural programs.

Administration is divided among subnational units including State of Idaho, State of Montana, State of Washington, Province of British Columbia, and numerous counties such as Spokane County, Washington and Kootenai County, Idaho. Cross-border water governance invokes the International Joint Commission and accords like the Columbia River Treaty (1964). Political representation includes members of the United States Congress from regional districts and members of the Legislative Assembly of British Columbia from interior ridings; Indigenous governance engages with entities recognized under the Indian Act and modern treaty processes such as the British Columbia Treaty Process.