The Mound Builders were Native American tribes that lived in the Midwest between 3000 BC and the 1700s who built thousands of earthen mounds for religious ceremonies, burials, and civic centers. One of the largest mounds, located in Ohio, was over 1,200 feet long and 20 feet wide. The largest Mound Builder city, Cahokia near St. Louis, was populated between 700-1400 AD and had a large pyramid mound at its center, surrounding a city of 10,000-20,000 people with rich cultural features.

1. Early Americans Chapter 1.1