Oregon Country was a large region of the Pacific Northwest of North America that was subject to a long dispute between the United Kingdom and the United States in the early 19th century. The boundaries of the area, which had been created by the Treaty of 1818 without recognizing indigenous claims to the area, consisted of the land north of 42° N latitude, south of 54°40′ N latitude, and west of the Rocky Mountains down to the Pacific Ocean and east to the Continental Divide. Article III of the 1818 treaty gave joint control to both nations for ten years, allowed land to be claimed, and guaranteed free navigation to all mercantile trade. However, both countries disputed the terms of the international treaty. Oregon Country was the American name while the British used Columbia District for the region. Meanwhile, Indigenous nations had lived in the area since time immemorial, though with little legal recognition in the American and British legal systems. Evidence along the Salmon River shows people lived there at least 16,000 years ago, and may have populated the continent after migrating along the Pacific Coast, then following up the Columbia River into the interior.

The Pacific Northwest (PNW), sometimes referred to as Cascadia, is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common conception includes the U.S. states of Oregon, Washington, northern Idaho, and the Canadian province of British Columbia. Some broader conceptions reach north into Alaska and Yukon, south into northern California, and east into western Montana. Other conceptions may be limited to the coastal areas west of the Cascade and Coast mountains.