Manifest Destiny: The Idea That Drove America Across a Continent

In 1845, a journalist named John O'Sullivan wrote that it was America's manifest destiny to overspread the continent allotted by Providence for the free development of our yearly multiplying millions. The phrase caught on immediately because it gave a respectable name to something the country was already doing and had been doing for decades: moving west, claiming land, displacing whoever was already there.

The Louisiana Purchase of 1803 had doubled the size of the United States overnight. Jefferson bought it from Napoleon for fifteen million dollars and was somewhat uncertain about its constitutionality, but he bought it. The Lewis and Clark expedition that followed was partly scientific, partly military reconnaissance, and partly a signal that America intended to understand and eventually occupy this vast interior.

Texas, California, the Oregon Territory, the Mexican Cession after the Mexican-American War — one by one, the pieces fell into place. By 1853, with the Gadsden Purchase, the continental United States had essentially reached its current borders. In less than a century, the country had grown from a strip of Atlantic seaboard settlements to a nation spanning from ocean to ocean.

The ideology of Manifest Destiny wove together several strands of American self-conception. There was Protestant Christianity's notion of a divinely chosen people. There was Enlightenment progressivism — the belief that civilization was advancing and that its advance was good. There was democratic ideology — the claim that republican self-government was superior to other forms and therefore deserved to spread. And underneath all of it was land hunger, pure and often ruthless.

The consequences for the people who were already on this land were catastrophic. Native American nations were removed, confined, decimated by disease and war and starvation, and finally reduced to a fraction of their former population and territory. The Trail of Tears, in which the Cherokee and other nations were forcibly marched from their homelands in the 1830s, killed thousands. It was national policy, endorsed by President Andrew Jackson, cheered by white settlers who wanted the land.

The Mexican-American War added further complication. The war was controversial even at the time. Abraham Lincoln, then a congressman, challenged Polk's justification for it. Ulysses Grant, who fought in it and won distinction, later called it one of the most unjust wars ever waged by a stronger nation against a weaker one.

None of this stopped the expansion, and few Americans at the time experienced much tension between their democratic values and the methods of expansion. Manifest Destiny worked precisely because it made expansion feel like destiny rather than choice, like Providence rather than policy. The belief that you are fulfilling a divine plan is among the most reliable ways humans have found to avoid examining what the plan actually costs.