Washita massacre in the context of Cheyenne, Oklahoma

Population figures for the Indigenous peoples of the Americas before European colonization have been difficult to establish. Estimates have varied widely from as low as 8 million to as many as 100 million, though by the end of the 20th Century, many scholars gravitated toward an estimate of around 50 million people.

The monarchs of the nascent Spanish Empire decided to fund Christopher Columbus' voyage in 1492, leading to the establishment of colonies and marking the beginning of the migration of millions of Europeans and Africans to the Americas. While the population of European settlers, primarily from Spain, Portugal, France, England, and the Netherlands, along with African slaves, grew steadily, the Indigenous population plummeted. There are numerous reasons for the population decline, including exposure to Eurasian diseases such as influenza, pneumonic plagues, and smallpox; direct violence by settlers and their allies through war and forced removal; and the general disruption of societies. Scholarly disputes remain over the degree to which each factor contributed or should be emphasized; some modern scholars have categorized it as a genocide, claiming that deliberate, systematic actions by Europeans were the primary cause. Traditional interpretation of the decline by scholars have disputed this characterization, maintaining that incidental disease exposure was the primary cause. This is supported by evidence where 50-80 percent of the population died from waves of diseases caused by Europeans in places such as Mexico in the 16th century.