Oregon Territory
United States 
Oregon Territory
Between 1818 and 1846 the portion of the 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 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. Finally, on 14 February 1959 part of the Oregon Territory split off into the current Oregon state boundaries, and was formed and admitted into the Union.