Big Muddy River Southern Illinois with "loess", fine grained, wind born deposits. At the edge of the floodplain, dunes, called "loess hills", formed. The Pine Hills are loess hills standing several hundred feet above the floodplain. Prior to the construction of Rend Lake, much of the ancient lake bed was swamp: a forested area that was covered by water through most of the winter, and during wet summers. When the Big Muddy flooded, the water covered the flat bottom of the ancient lake bed for miles either direction from the meandering channel. The upper reaches of the Big Muddy are near Dix, Illinois.
Fox River (Illinois River tributary) near the Fox River included the Potawatomi, Sac, and Fox tribes. The Fox River has 15 dams, including McHenry Dam, which raises the river slightly to maintain depth in the Chain O'Lakes in northern Illinois, and a hydroelectric dam near Ottawa. In the winter, bald eagles can be found nesting along the banks. Early in the history of Illinois, the Fox River provided water for the Illinois and Michigan Canal via a feeder canal, allowing the canal to pass over the Fox River on an aqueduct. In 1996, a flood damaged the Farnsworth House in Illinois, a residence designed by