Columbia Plateau in the context of "Tri-Cities, Washington"

The Snake River is a major river in the interior Pacific Northwest region of the United States. About 1,080 miles (1,740 km) long, it is the largest tributary of the Columbia River, which is the largest North American river that empties into the Pacific Ocean. Beginning in Yellowstone National Park, western Wyoming, it flows across the arid Snake River Plain of southern Idaho, the rugged Hells Canyon on the borders of Idaho, Oregon and Washington, and finally the rolling Palouse Hills of southeast Washington. It joins the Columbia River just downstream from the Tri-Cities, Washington, in the southern Columbia Basin.

The river's watershed, which drains parts of six U.S. states, is situated between the Rocky Mountains to the north and east, the Great Basin to the south, and the Blue Mountains and Oregon high desert to the west. The region has a long history of volcanism; millions of years ago, Columbia River basalts covered vast areas of the western Snake River watershed, while the Snake River Plain was a product of the Yellowstone volcanic hotspot. The river was further altered by catastrophic flooding in the most recent Ice Age, which created such features as the Snake River Canyon and Shoshone Falls.

The Wallowa River is a tributary of the Grande Ronde River, approximately 55 miles (89 km) long, in northeastern Oregon in the United States. It drains a valley on the Columbia Plateau in the northeast corner of the state north of Wallowa Mountains.

The Wallowa Valley was home to Chief Joseph's band of the Nez Perce Tribe. Chief Joseph asked the first white settlers to leave when they arrived in 1871. The U.S. government expelled the tribe and seized their property and livestock in 1877, when non-Indian farmers and ranchers wanted to settle the fertile Wallowa valley. The tribe was barred from returning to their homeland by the government after repeated petitions. The tribal members were shipped in unheated box cars to Indian Territory (now Oklahoma) to be placed in a prisoner-of-war camp never to see their home again.

A kame, or knob, is a glacial landform, an irregularly shaped hill or mound composed of sand, gravel and till that accumulates in a depression on a retreating glacier, and is then deposited on the land surface with further melting of the glacier. Kames are often associated with kettles, and this is referred to as kame and kettle or knob and kettle topography. The word kame is a variant of comb (kame, or kaim is the Old Scottish word meaning 'comb'), which has the meaning "crest" among others. The geological term was introduced by Thomas Jamieson in 1874.

According to White, "kames were formed by meltwater which deposited more or less washed material at irregular places in and along melting ice. At places the material is very well washed and stratified; at others it is more poorly washed, with inclusions of till masses that fell from ice but were covered before they were completely washed. Kame gravels thus tend to be variable and range from fine to coarse grained and even to cobbly and boulder."

The Interior Plateau comprises a large region of the Interior of British Columbia, and lies between the Cariboo and Monashee Mountains on the east, and the Hazelton Mountains, Coast Mountains and Cascade Range on the west. The continuation of the plateau into the United States is known there as the Columbia Plateau.

Physiographically, the Interior Plateau is a section of the larger Northern Plateaus province, which in turn is part of the Intermontane Plateaus physiographic division.

The Nez Perce (/ˌnɛz ˈpɜːrs, ˌnɛs -/ ; autonym in Nez Perce: nimíipuu, meaning 'we, the people') are an Indigenous people of the Plateau who still live on a fraction of the lands on the southeastern Columbia River Plateau in the Pacific Northwest. This region has been occupied for at least 11,500 years.

Members of the Sahaptin language group, the Nimíipuu were the dominant people of the Columbia Plateau for much of that time, especially after acquiring the horses that led them to breed the Appaloosa horse in the 18th century.