The earliest known inhabitants of what is now the United States are thought to have arrived in Alaska by crossing the Bering land bridge, at least 14,000 - 30,000 years ago.[11] Some of these groups migrated south and over time spread throughout the Americas. These were the ancestors to modern Native Americans in the United States and Alaskan Native peoples, as well as all indigenous peoples of the Americas.

Many indigenous peoples were semi-nomadic tribes of hunter-gatherers; others were sedentary and agricultural civilizations. Many formed new tribes or confederations in response to European colonization. Well-known groups included the Huron, Apache Tribe, Cherokee, Sioux, Delaware, Algonquin, Choctaw, Mohegan, Iroquois (which included the Mohawk nation, Oneida tribe, Seneca nation, Cayuga nation, Onondaga and later the Tuscarora tribe) and Inuit. Though not as technologically advanced as the Mesoamerican civilizations further south, there were extensive pre-Columbian sedentary societies in what is now the US. The Iroquois had a politically advanced and unique social structure that was at the very least inspirational if not directly influential to the later development of the democratic United States government, a departure from the strong monarchies from which the Europeans came.[cit