Manifest Destiny is a phrase used by leaders and politicians in the 1840s to argue for the continental expansion by the United States. Writing in the Democratic Review, the editor John O’Sullivan stated it was “our manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions.” This slogan revitalized a sense of “mission” and national God-given destiny for Americans. It was used as a justification for the first foreign war–against Mexico– fought by the newly formed United States.
"Manifest Destiny," painting by John Gast, 1872.
People in the United States felt it was their mission to extend the “boundaries of freedom” by imparting their idealism and belief in democratic institutions to others who were considered capable of self-government. Excluded were those people whose cultural differences were seen with paternalism or bias, such as Native American people and those of non-European origin.