Manifest Destiny was an idea that came up during the United States' period of Expansion during the early 1800's. It was believed that God gave the country the right to expand its borders all the way to the Pacific Ocean due to their belief of their racial superiority over the native & Spanish peoples. Manifest Destiny also provided the reason for the United States to go to war with Mexico to gain more territory and lands. Early supporters later changed their minds about Manifest Destiny because it gave a reason to expand the institution of Slavery within the Southern Territories that had now been acquired. Manifest Destiny was also brought about by the economic opportunities in the West with the fur trade and other things.