When Donald Trump first suggested that the United States should purchase Greenland, the reaction in Washington was disbelief mixed with ridicule. The United States, it had seemed, long ago settled its borders. Territorial expansion belonged to a different era.
Yet in the longer arc of American history, expansion has been quite normal. For much of the nation’s first century and a half, Americans debated not whether the United States should grow, but where and by what means. The idea that borders might shift was a routine feature of statecraft. So why does the idea now seem so strange?
Immediately after landing in North America, European colonists began spreading out. When the United States declared its independence, one of the Founding Fathers’ motivations was to move into new lands that Great Britain had closed to settlement. In the nation’s earliest days, its leaders did not treat its new borders as fixed. They were open to negotiation, purchase, conquest, and sometimes improvisation.
That assumption shaped the nation’s foreign policy from its earliest days. Before the Declaration of Independence, the Continental Congress authorized an invasion of Quebec, hoping to add another colony to the union. The effort failed, but it reflected the assumption that territorial expansion was both legitimate and desirable when it served the nation’s interests.
A few years later, the nation doubled its size through the Louisiana Purchase. The War of 1812 included another attempt to seize Canada. By the 1840s, the United States had extended its reach across the continent through a combination of negotiation and war. Political debates during this period tended not to question whether expansion was appropriate, but instead its extent. Should the nation take all of Mexico or only part? Was Cuba or Canada a better target? Should expansion continue into Central America?
For the first half of its independent history, expansion was simply how the United States operated.
At times, this ambition took forms that today seem strange. Private adventurers known as filibusters launched armed expeditions into Latin America to try to bring new territories under American control. After the Civil War, policymakers considered annexing the Dominican Republic, Haiti, Greenland, and various Pacific islands. Some of these proposals now seem implausible, but only because history turned out differently. The annexations of Alaska and Hawaii appear natural in hindsight, though they were once contested and uncertain.
By the late nineteenth century, however, American expansion had begun to change. The United States continued to acquire territory, including Puerto Rico, Guam, and the Philippines after the Spanish-American War. But this growth was becoming more selective. Policymakers increasingly sought limited strategic positions rather than large territorial additions. Opportunities for expansion were sometimes declined. Other territorial claims were abandoned.