It refers to the idea that the nation had the right and duty to expand westward and occupy all of the land between the Atlantic and Pacific oceans.
The concept was first articulated by journalist John O'Sullivan in an 1845 issue of the "United States Magazine and Democratic Review". O'Sullivan wrote that the American people had a "manifest destiny to overspread and to possess the whole of the continent which Providence has given us for the development of the great experiment of liberty and federated self-government."
Manifest destiny was used to justify the United States' expansion into the West, including the Mexican-American War (1846-1848) and the acquisition of California and the Southwest. The ideology was also used to justify the displacement and removal of Native American tribes.
