In the United States, Native Americans (also known as American Indians, Amerindians, Indigenous Americans or simply Indians; see §Terminology differences) are people descended from the Pre-Columbian indigenous population of the land within the country's modern boundaries. These peoples were composed of numerous distinct tribes, bands, and ethnic groups, and many of these groups survive intact today as partially sovereign nations.

Since the end of the 15th century, the migration of Europeans to the Americas has led to centuries of population, cultural, and agricultural transfer and adjustment between Old and New World societies, a process known as the Columbian exchange. Most Native American groups had historically preserved their histories by oral traditions and artwork, which has resulted in the first written sources on the conflict being authored by Europeans.[3]

At the time of first contact, the indigenous cultures were quite different from those of the proto-industrial and mostly Christianimmigrants. Some of the Northeastern and Southwestern cultures in particular were matrilineal and operated on a more collective basis than the Europeans were familiar with. The majority of Indigenous American tribes maintained their hunting grounds and agricultural lands for use of the entire tribe. Europeans at that time had patriarchal cultures and had developed concepts of individual property rights with respect to land that were extremely different. The differences in cultures between the established Native Americans and immigrant Europeans, as well as shifting alliances among different nations in times of war, caused extensive political tension, ethnic violence, and social disruption. Even before the European settlement of what is now the United States, Native Americans suffered high fatalities from contact with European diseases spread throughout the Americas by the Spanish to which they had yet not acquired immunity. Smallpox epidemics are thought to have caused the greatest loss of life for indigenous populations, although estimates of the pre-Columbian population of what today constitutes the U.S. vary significantly, from one million to eighteen million.[4][5]