A popular idea known as "Manifest Destiny" swept America during the Nineteenth Century. This idea promoted the belief that the nation had a divine mission to spread from the Atlantic coast to the Pacific coast, opening the continent to American Settlement. James K. Polk was elected the eleventh U.S. President in 1844 because of his support for Manifest Destiny. Polk acquired the Oregon Territory from Great Britain by treaty, and most of the American Southwest, including California, New Mexico, and Arizona, by provoking a war with Mexico. By the end of Polk's administration, Manifest Destiny had been achieved.