Complex sentence: Once over the mountain, the Warpath crossed lower Chattanooga Valley to what archaeologists refer to as the Citico site, which was for several hundred years the pre-eminent town in the early period of the Mississippian culture in East Tennessee (until around 1200).
Split into simpler sentences: Once over the mountain, the Warpath crossed lower Chattanooga Valley to what archaeologists refer to as the Citico site. For several hundred years this was the pre-eminent town in the early period of the Mississippian culture in East Tennessee (until around 1200).