At http://www.examiner.com March 7th … there is a lengthy article about mounds in the US – mainly in the Mississipi, Ohio and Tenessee river valleys, and the lower south east region. The earliest mound is an earth ring 300 feet in diameter dating back to 3500BC. Between 2500 and 1200BC shell mounds or rings were built along the south Atlantic coast (in Georgia for example). Between 1500BC and 1000AD mounds appeared inland – made of earth and fresh water mussel shells. Between 800BC and 200BC the Adena culture constructed 100s of dome and cone shaped mounds in the Ohio river basin. At the same time, in the SE, other people built burial cairns and effigies out of field stones. Between 200BC and 500AD the Hopewell culture build mounds and earthworks. Over time they grew from simple cones into huge geometric designs. In the lower SE there were permanent communities and ceremonial centres – including mounds resembling pyramids. The architecture was similar to that of Mexico and may indicate migration – or contact and cross fertilisation of culture. Between 300 and 700AD, in southern Florida, large towns with earth structures evolved – with evidence of some influence or cultural similarities with the Maya. In 900AD a huge trading centre was built in Georgia – and again there were similarities with the Maya, particularly it’s architecture. After 1000AD a huge mound was built near modern St Louis (Cahokia) and other large towns developed in Tuscaloosa. Between 1250 and 1300AD there was a culture shift as mounds became smaller – but the number of towns grew dramatically. Mounds ceased to be built in around 1600AD.