Oregon Territory

Refers to the region in North America that now encompasses the present day states of Washington, Oregon, Idaho, and parts of Montana and Wyoming.

Between 1818 and 1846 the portion of western North America that currently covers the states of Oregon, Washington, Idaho and western portions of Montana and Wyoming was part of a large Oregon Country "disputed area" that was claimed and occupied by both the United States and Great Britain.

The Oregon Treaty, signed by both countries in Washington, DC on 15 June 1846, ended the dispute. The Treaty established a border at the 49th parallel to divide Oregon Country between British North America (north of the 49th) and the United States (south of the 49th). U.S. sovereignty over their “Oregon Territory” region was established, but the area was temporarily left unorganized. Two years later, the Oregon Territory was finally recognized by the United States. The area officially existed as a U.S. territory from 14 August 1848 (Act to Establish the Territorial Government of Oregon), to 1853.

On the 2nd of March 1853 the entire northern part of the territory was split off and organized into Washington Territory.

On 14 February 1859 part of the Oregon Territory split off into the current Oregon state boundaries, and was formed and admitted into the Union as a state. On that date, the eastern portions of the Oregon Territory, including southern Idaho, portions of Wyoming west of the continental divide, and a small portion of present-day Montana were annexed to the Washington Territory. The remaining portions of Idaho and parts of Montana and Wyoming were ceded to the Nebraska and Idaho Territories in 1861 and 1863.

Nebraska was admitted to the Union as a state on 1 March 1867.

Montana was admitted to the Union as a state on 8 November 1889.

Washington was admitted to the Union as a state on 11 November 1889.

Idaho was admitted to the Union as a state on 3 July 1890.

Wyoming was admitted to the Union as a state on 10 July 1890.

Online resources
 * Treaty between Her Majesty and the United States of America for the settlement of the Oregon boundary : signed at Washington, June 15, 1846 Canadiana