Lesson 1: Native Americans and Cahokia. Long before Europeans, the land we call Illinois was home to Native peoples. The Illiniwek lived across the region. Near the Mississippi River, Cahokia was one of the largest cities in North America. Thousands of people lived there. They built huge earthen mounds for ceremonies and leaders. Cahokia declined by the 1300s, but later tribes including the Illiniwek continued to live and trade here.