Indigenous peoples of the Northwest Plateau

Indigenous peoples of the Northwest Plateau, also referred to by the phrase Indigenous peoples of the Plateau, and historically called the Plateau Indians (though comprising many groups) are Indigenous peoples of the Interior of British Columbia, Canada, and the non-coastal regions of the Northwestern United States.

Their territories are located in the inland portions of the basins of the Columbia and Fraser Rivers. These tribes mainly live in parts of the Central and Southern Interior of British Columbia, northern Idaho, western Montana, eastern Washington, eastern Oregon, and northeastern California. The eastern flank of the Cascade Range lies within the territory of the Plateau peoples.

There are several distinguishing features that differentiate plateau culture from the surrounding native cultures. These include a high reliance on roots, such as biscuitroot and camas, as a food source, a high reliance on short duration salmon and eel runs, and long-term habitation of winter villages at fixed locations along rivers or lakes. There was a lack of social stratification and a lack of tribal organization beyond the village level.

In Canada, the greater part of the Interior Plateau was inhabited by Interior Salish peoples: the Lillooet tribe whose homelands are in the Lillooet River Valley; the Thompson First Nations, whose homelands are in the Fraser River Valley from Yale to Lillooet; the Secwepemc (Shuswap) of the Fraser River Valley from Lillooet to Alexandria, the upper parts of the Thompson River basin, and areas further east; the Okanagan of the Okanagan River Valley and its vicinity; also the Lakes people of the Arrow Lakes. The Kutenai tribe, who live in the southeastern parts of British Columbia and formerly extended to southwestern Alberta, speak an isolate language. Athapaskan-speaking people, the Chilcotin and Carrier, occupy the northernmost part of the Plateau region.

The First Nations of the Plateau were influenced by the First Nations of the Pacific Coast. The Plateau First Nations traded many goods with the Pacific Coast First Nations. The Pacific tribes believed in clan ancestors which were adopted by the Interior Salish groups, but they did not adopt the social system.

In the United States, Interior Salish people inhabited the Columbia River and its tributaries above Priest Rapids, near present-day Mattawa. Sahaptin people inhabited the Columbia River and its tributaries between Priest Rapids and Celilo Falls near the Dalles, Oregon and up the Snake River to near the Washington - Idaho border. The Nez Perce inhabited the Clearwater and Salmon River basins and the Snake river through Hells Canyon. The Cayuse homeland is the Blue Mountains and the valleys of the rivers that flow from them. The Molala inhabited the eastern side of the cascade mountains in Oregon. The Klamath people inhabited the upper Klamath River basin and had close contact with people from the California cultural area, though their lifestyle and language were more characteristic of plateau culture.

The Columbia River below Celilo Falls was inhabited by Chinook people. Chinook people on the lowest portion of the Columbia are considered part of the Northwest Coast. Sahaptin groups also lived in Western Washington on the Mashel River and upper Cowlitz River. The Willamette Valley was inhabited by the Kalapuya people. Having no major salmon run, their culture was somewhat different from other plateau people, maintaining oak savannas similar to many California natives.

While plateau people kept no written records, the prehistory of the plateau region can be partially reconstructed by a combination of oral traditions, linguistics and archeological evidence. There is archeological evidence of human presence on the plateau for at least 12,000 years. The Marmes Rockshelter and Kennewick Man are two examples of early human presence. Over time human technologies adapted to the unique environment. Earth ovens near camas meadows have been found that are up to 8,000 years old. Around 4,000 years ago, there was a shift in the archeological record from small bands to larger semi-sedentary villages, and a shift towards root processing tools, hallmarks of plateau culture.