Big Muddy River Here the outline of the Wisconsinan Era lake bed is evident in what were the northern reaches of the ancient lake, where the lake bed was only a few hundred feet wide. The steep Illinoian hills are suddenly truncated where they meet the flat bottom of the Wisconsinan Era lake bed. Here the tributaries of the Big Muddy are tiny, intermittent streams, meandering though these narrow valleys at the headwaters. The Big Muddy basin contains a significant portion of the planet's coal reserves. Most of this is hidden under its deep mud. At a few places the river has eroded
Fox River (Illinois River tributary) area. From the chain, the river flows generally southward for , until it joins the Illinois River at Ottawa. Illinois towns and communities that are on the Fox River include (from north to south): Fox Lake, Johnsburg, McHenry, Holiday Hills, Island Lake, Burtons Bridge, Port Barrington, Cary, Fox River Grove, Algonquin, Carpentersville, West Dundee, East Dundee, Elgin, South Elgin, St. Charles, Geneva, Batavia, North Aurora, Aurora, Montgomery, Oswego, Yorkville, Plano, Millington, Sheridan and Ottawa. Collectively, the area surrounding the Fox River is known as the Fox Valley. Around 1 million people live in this area. Native American tribes that lived