The last of five general cultural stages proposed by G. Willey and P. Phillips in 1958 as a framework for the study of ancient communities in the Americas. The Post‐Classic, which directly follows the Classic, embraces communities that can be identified with an imperialistic state organization. Its application is therefore highly restricted within Mesoamerica and the central and west coasts of South America, where such societies were present in the period from about ad 900 down to the Spanish conquest in the 16th century. During this time the high civilizations of earlier periods declined and changed as in a cyclical pattern of conquest and collapse. Many of the societies that lived in this period were strongly militaristic and warfare was widespread. The principal Post‐Classic groups of the period were the Inca, Toltec, and Aztec.