The Oregon Historical Society (OHS) is an organization that encourages and promotes the study and understanding of the history of the Oregon Country, within the broader context of U.S. history. Incorporated in 1898, the Society collects, preserves, and makes available materials of historical character and interest, and collaborates with other groups and individuals with similar aims. The society operates the Oregon History Center that includes the Oregon Historical Society Museum in downtown Portland.

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.