Hopewell culture (200 BCE – 400 CE): The Hopewell people were a highly advanced culture that flourished in the Ohio River Valley. They built large ceremonial earthworks, including the Hopewell Mound Group in Ohio, which is one of the largest prehistoric earthworks in the world.
Mississippian culture (800 – 1500 CE): The Mississippian people were the last major mound-building culture in the eastern United States. They built large ceremonial centers, including the Cahokia Mounds in Illinois, which is the largest prehistoric earthwork in the Americas.