Location of the American Bottom in the Central Mississippi River Valley.
|In central North America three great rivers, the Missouri, the Illinois, and the Mississippi merge. Just south of their confluence, on the eastern side of the Mississippi River lies an expansive floodplain. This area across from St. Louis, Missouri between Alton, Illinois to the north and Chester, Illinois to the south, is a patchwork of large farms, urban centers, and industrial parks crisscrossed by ribbons of levees and roads. These modern developments have significantly altered the physical and biological environments and mask the natural features of this great North American river floodplain known as the American Bottom.|