James K. Polk ended a binary dispute with the British in 1846 with what treaty?
James K. Polk:  During his presidency, the United States expanded significantly with the annexation of Republic of Texas, the Oregon Treaty, and the conclusion of the Mexican-American War. Oregon Treaty: The Oregon Treaty is a treaty between the United Kingdom and the United States that was signed on June 15, 1846, in Washington, D.C. Signed under the presidency of James K. Polk, the treaty brought an end to the Oregon boundary dispute by settling competing American and British claims to the Oregon Country; the area had been jointly occupied by both Britain and the U.S. since the Treaty of 1818.
The Oregon Treaty