Archaeological evidence indicates that people of the Plaquemine culture, an elaboration of the Coles Creek culture, had lived in the Natchez Bluffs region since at least as long ago as 700 CE. The Natchez Bluffs are located along the east side of the Mississippi River in present-day Mississippi. During the late prehistoric era, around 1500, Plaquemine-culture people occupied territory from the Big Black River in the north to about the Homochitto River in the south. The Plaquemine people built many platform mounds, including Emerald Mound, the second-largest pre-Columbian structure in North America north of Mexico. Emerald Mound was an important ceremonial center.