Manifest Destiny was the belief that the Unite States was destined to expand from the Atlantic seaboard to the Pacific Ocean; it has also been used to advocate for or justify other territorial acquisitions. Advocates of Manifest Destiny believed that expansion was not only good, but that it was obvious ("manifest") and certain ("destiny"). Originally a political catch phrase of the 19th century, "Manifest Destiny" eventually became a standard historical term, often used as a synonym for the expansion of the United States across the North American continent.