The first Americans arrived on the Great Plains thousands of years ago. Historically, the Great Plains were the range of the Blackfoot, Crow, Sioux, Cheyenne, Arapaho, Comanche, and others. Eastern portions of the Great Plains were inhabited by tribes who lived at Etzanoa and in semi-permanent villages of earth lodges, such as the Arikara, Mandan, Pawnee, and Wichita. The introduction of corn around 800 CE allowed the development of the mound-building Mississippian Culture along rivers that crossed the Great Plains and that included trade networks west to the Rocky Mountains. Mississippians settled the Great Plains at sites now in Oklahoma and South Dakota.