Manifest Destiny was a 19th century philosophy in the United States that advocated the settlement of the American West and the extension of the USA "from sea to shining sea" (from the Atlantic to the Pacific). The idea, promoted by the conservative US Democratic Party and opposed by the liberal US Whig Party, led to the USA justifying the Mexican-American War and its division of Oregon with the United Kingdom. The ideology's goals essentially meant that slavery would be extended to new US territories and that the Native Americans and non-Americans would have to be forcibly removed or subjugated, leading to a series of wars with the Native Americans and clashes with Mexico and the Mormons. By 1848, the goal of expanding to the Pacific had been achieved, with the USA annexing California.