In 1844 the Oregon Territory spanned the modern states of Oregon, Idaho, and Washington, as well as the western coast of Canada up to the border of Russian Alaska. Both Great Britain and America claimed the territory.
President James K. Polk tapped into the public mood and the prevalent attitude of manifest destiny in the U.S. that called for expansion into Texas, California, and the entire Oregon territory. The northern boundary of Oregon was the latitude line of 54 degrees, 40 minutes. "Fifty-four forty or fight!" was the popular slogan that led Polk to victory against all odds.
Polk boldly declared to Great Britain that joint occupation would end within one year. The British were confident they could win, but by 1846 they were vastly outnumbered in Oregon by a margin of greater than six to one. In June of that year, Britain proposed splitting Oregon at the 49th parallel. Polk agreed to the compromise, and conflict was avoided.