On Day 3 of a grand tour we spent an afternoon at Cahokia Mounds State Historic Site in Illinois, outside of East St. Louis. Alas, upon arrival, we learned the visitor center and parts of the site are closed on Mondays — and it was Monday! The largest mound "Monks Mound" was accessible, and there were a fair number of informative signs around, so we were still able to get a good sense of what it was about. From the top of the mound one can see the skyline of St. Louis and the Gateway Arch.

The mound building civilization was active on both sides of the Mississippi River in the St. Louis area during the first millennium of the Common Era. Many of the built up earthen mounds are still extant, the various structures that topped them are gone, although careful archeological work gives some idea of what they may have been like. The "Monks" part of the name of that mound derives from a much later reuse by French Trappist Monks in the early 1800s.

Monks Mound is approximately 100 feet high, covers 14 acres and contains an estimated 22 million cubic feet of earth. All of this material would have been hand dug from "borrow pits" around the area and hand carried in baskets. The mound was built up in stages, creating multiple layers and terraces over the period from 950 to 1200 CE.

This was part of the Grand Tour 2016, a 5800 mile drive through flyover country!