USA HISTORY

Detailed explanation-1: -Originally Spain, Great Britain, Russia, and the United States claimed the territory. In 1819, under terms of the Transcontinental Treaty, Spain ceded its claims to the territory to the United States.

Detailed explanation-2: -The United States and Great Britain signed the Treaty of Oregon on June 15, 1846, ending 28 years of joint occupancy of the Pacific Northwest. The treaty established the 49th parallel as the border between the two countries.

Detailed explanation-3: -In 1846 Britain and the United States signed the Oregon Treaty, extending the international border between the U.S. and what would become Canada along the 49th parallel to the Strait of Georgia, and then out the Strait of Juan de Fuca.