One of the earliest identifiable cultures was the Clovis culture, with sites dating from some 13,000 years ago.
However, older sites dating back to 20,000 years ago have been claimed, some genetic studies estimate the colonization of the Americas dates from between 40,000 and 13,000 years ago.
Many pre-Columbian civilizations established hallmarks which included permanent settlements, cities, agriculture, civic and monumental architecture, major earthworks, and complex societal hierarchies.
Some of these civilizations had long faded by the time of the first permanent European colonies and the arrival of enslaved Africans (c.
Built about 1500 BCE, it is the centerpiece of a culture extending over 100 sites on both sides of the Mississippi, the Poverty Point site has earthworks in the form of six concentric half-circles, divided by radial aisles, together with some mounds. Mound building was continued by succeeding cultures, who built numerous sites in the middle Mississippi and Ohio River valleys as well, adding effigy mounds, conical and ridge mounds and other shapes.
The unstable climate led to widespread migration, with early Paleo-Indians soon spreading throughout the Americas, diversifying into many hundreds of culturally distinct tribes, the Paleo-Indians were hunter-gatherers, likely characterized by small, mobile bands consisting of approximately 20 to 50 members of an extended family.
These groups moved from place to place as preferred resources were depleted and new supplies were sought.
Paleo-Indian groups carried a variety of tools, these included distinctive projectile points and knives, as well as less distinctive implements used for butchering and hide processing.
The vastness of the North American continent, and the variety of its climates, ecology, vegetation, fauna, and landforms, led ancient peoples to coalesce into many distinct linguistic and cultural groups.