The Smallpox Epidemics

No weapon proved more devastating to the Native peoples of the Americas than disease. Having been separated from the rest of humanity for thousands of years, Indigenous Americans had no immunity to the Old World illnesses—smallpox above all, but also measles, influenza, and others—that arrived with European explorers and settlers. The microbes often raced ahead of the colonists themselves, carried along trade and travel routes, so that many communities were shattered by epidemics before they ever saw a European face.

The death toll was almost beyond comprehension. Across the hemisphere, disease is estimated to have killed as much as ninety percent of the pre-contact Native population over the first century and a half of contact—a demographic catastrophe with few parallels in human history. Whole nations vanished or were so reduced that they could no longer defend their lands. Smallpox struck again and again into the nineteenth century, including a terrible epidemic that swept the Great Plains in 1837 and all but destroyed the Mandan. The depopulation hollowed out the continent the colonists were claiming, making conquest far easier than it would otherwise have been.