Oh, check out Cahokia Mounds, and the culture up and down the Illinois River, especially around Kampsville, Illinois. Also the Serpent Mound and related mounds in Ohio and the animal mounds in Wisconsin. There are mounds in Arkansas (big bunch down there) and clear to the Gulf. There is considerable evidence that a healthy trade existed between the "Anasazi", the peoples of the Pacific Northwest, the Plains people, the Mississippian culture, and the Woodland cultures of the Eastern US. Evidence includes, but is not limited to, cowrie shells and copper.

If you want to investigate something, look into the similarities between the Clovis points and those found in Neolithic France -- and the Western Shore of Maryland.