Dixon Springs State Park has 3-miles on mountain biking/hiking trails (Bluff Trail, Pine Tree, Oak Tree and Red Dog). See the map for the mountain biking trails in this area. These trails connect into the Lake Glendale mountain bike trail system.

Rend Lake has 6-miles of mountain bike trails that take you through an abandoned campground area. Check out this map to see where this area is. An additional 6-miles is said to be planned for creation.

Possibly the best mountain biking trails in southern Illinois, located at the Southern Illinois University Touch of Nature Center off Giant City Road, there is about 12-miles of pro-made mountain bike trails with a goal of about 30-miles. Races are often held on this trail and the organization does close it when wet. Don’t miss out on these trails, they’re awesome. A small day-fee is required or you can spend $40 for an annual permit.

The Shawnee National Forest has other places to ride mountain bikes in – open forest roads.

This is what the US Forest Service says about this allowance:
“In other parts of the Forest there are restrictions prohibiting mountain bikes from traveling off-road, in natural areas and in other non-motorized areas. This means mountain bikes are allowed only on roads. Generally, roads within the Shawnee National Forest consist of either dirt or gravel. In this area, state highways are narrow and have heavy truck use. Therefore, use extra caution when riding along these routes.”

So if the road is open to motor-vehicle use of any kind, bicycle are allowed automatically. A bicycle is considered a legal vehicle in the State of Illinois and across the country. See this map for a list of Forest Service Roads on the East Side and this map for the West Side roads.