Lewis and Clark expedition wintered in area, 1805–1806. Treaty of 1818 between U.S. and England provided decade of joint rights to area. Major immigration to area from existing U.S. states commenced, 1839. Oregon Trail used as main route to area, beginning 1841. In 1844, Oregon Country included all or part of present-day states of Oregon, Idaho, and Washington, as well as British Columbia, Canada. Area disputed between United States and United Kingdom until Oregon Treaty, 1846. Formally established as U.S. territory, 1848. On 20 Feb. 1844, JS instructed Twelve Apostles of Church of Jesus Christ of Latter-day Saints to send delegation to investigate area for possible settlement; seven men volunteered to serve on expedition, which ultimately did not occur. JS signed memorials to U.S. president [John Tyler] and Congress, 1844, urging protection of Americans migrating to western regions of North America.