A small gorge near Ozark, Illinois. Popular for rock climbing and, unfortuneately, horse packing, which interferes with the climbers and tears up the trails.
It's best known for its sport climbs, but has some very nice trad climbs. Most of the roped climbs are 12 to 18 m (35' to 60') high. The hardest sport climbs there are probably mid-5.13s (French 8a)
While bouldering has been happening there for quite a while, it has been growing recently. Waddling packs of giant playing cards can be seen shuffling from rock to rock with the cry of 'Dude!" echoing through the trees.
It's about a 2 hour drive from St. Louis, MO and about a 6 hour drive from Chicago.