This photo of Towosahgy State Historic Site in Mississippi County, within the New Madrid Floodway, reveals perhaps the real reason that Mississippian culture native Americans built mounds up and down the middle Mississippi Valley at Cahokia, St. Louis, the Bootheel and counties adjacent to the big river:

One of the last remaining Indian mounds in “Mound City”, Sugar Loaf Mound at 4420 Ohio Street, near the Mississippi River, was purchased July 31 by the Osage Nation of Pawhuska, Oklahoma. Sale price is said to be $230,000.