Many pre-Columbian civilizations established characteristics and hallmarks which included permanent or urban settlements, agriculture, civic and monumental architecture, and complex societal hierarchies. Some of these civilizations had long faded by the time of the first permanent European and African arrivals (ca. late 15th–early 16th centuries), and are known only through oral history and archaeological investigations. Others were contemporary with this period, and are also known from historical accounts of the time. A few, such as the Maya, Olmec, Mixtec, and Nahua peoples, had their own written records. However, the European colonists of the time viewed such texts as heretical, and much was destroyed in Christian pyres. Only a few hidden documents remain today, leaving contemporary historians with glimpses of ancient culture and knowledge.
According to both indigenous American and European accounts and documents, American civilizations at the time of European encounter possessed many impressive accomplishments. For instance, the Aztecs built one of the most impressive cities in the world, Tenochtitlan, the ancient site of Mexico City, with an estimated population of 200,000. American civilizations also displayed impressive accomplishments in astronomy and mathematics. Inuit, Alaskan Native, and American Indian creation myths tell of a variety of originations of their respective peoples. Some were "always there" or were created by gods or animals, some migrated from a specified compass point, and others came from "across the ocean".