Olmec tomb The ancient Olmec civilization is believed to have been centred around the southern Gulf Coast of Mexico area (today the states of Veracruz and Tabasco) - further south east than the heart of the Aztec empire. The Olmec culture developed in the centuries before 1200BC (BCE), and declined around 400BC.
A Missisippian culture town in modern Kincaid, IL. Circa 1200 AD. While Cahokia was certainly the grandest of the Mississippian cities and towns, even the lesser settlements were impressive in their own right with earthworks supporting temples and wealthy residents' houses and palisade walls. According to conquistador De Soto, at each town, one could always see at least two or three more in the distance, so dense was the population.