Manifest destiny was a widely held cultural belief in the 19th-century United States that American settlers were destined to expand across North America. There are three basic themes to manifest destiny:
- The special virtues of the American people and their institutions
- The mission of the United States to redeem and remake the west in the image of the agrarian East
- An irresistible destiny to accomplish this essential duty
Newspaper editor John O'Sullivan is generally credited with coining the term manifest destiny in 1845 to describe the essence of this mindset; other historians believe the unsigned editorial titled "Annexation" in which it first appeared was written by journalist and annexation advocate Jane Cazneau.
Historians have emphasized that "manifest destiny" was a contested concept—Democrats endorsed the idea but many prominent Americans (such as Abraham Lincoln, Ulysses S. Grant, and most Whigs) rejected it. Historian Daniel Walker Howe writes, "American imperialism did not represent an American consensus; it provoked bitter dissent within the national polity ... Whigs saw America's moral mission as one of democratic example rather than one of conquest."
The term was used by Democrats in the 1840s to justify the Mexican–American War and it was also used to negotiate the Oregon boundary dispute. Historian Frederick Merk says manifest destiny always limped along because of its internal limitations and the issue of slavery in the United States, and never became a national priority. By 1843, former U.S. President John Quincy Adams, originally a major supporter of the concept underlying manifest destiny, had changed his mind and repudiated expansionism because it meant the expansion of slavery in Texas.