Pre-Columbian Aztec society was a highly complex and stratified society that developed among the Aztecs of central Mexico in the centuries prior to the Spanish conquest of Mexico, and which was built on the cultural foundations of the larger region of Mesoamerica. Politically, the society was organized into independent city-states, called altepetls, composed of smaller divisions (calpulli), which were again usually composed of one or more extended kinship groups. Socially, the society depended on a rather strict division between nobles and free commoners, both of which were themselves divided into elaborate hierarchies of social status, responsibilities, and power. Economically the society was dependent on agriculture, and also to a large extent on warfare. Other economically important factors were commerce, long distance and local, and a high degree of trade specialisation.