Taum Sauk Mountain in Reynolds County crowns the St. Francois Mountains, the oldest exposed bedrock in the United States, dating back 1.5 billion years to Precambrian volcanic activity. At 1,772 feet, it is Missouri's highest point — a gentle summit by any measure, but the surrounding landscape of the Ozark Trail and Taum Sauk Mountain State Park is far more dramatic than the elevation suggests. The rocks here are ancient rhyolite, pink and weathered, jutting from the thin Ozark soil in formations known locally as "shut-ins" where streams squeeze through resistant rock in a series of pools and rapids.

The Taum Sauk section of the Ozark Trail is a 12-mile loop from the state park that visits both the summit and Mina Sauk Falls (132 feet — Missouri's tallest waterfall) before passing through the Shut-Ins at Johnson's Shut-Ins State Park. Most hikers combine this with a swim at the natural waterslides of Johnson's Shut-Ins, where the East Fork Black River rushes through red rhyolite channels. The loop hike is rated moderate; the Shut-Ins add a full half-day of swimming and exploration.

Taum Sauk Mountain State Park is free to visit. Johnson's Shut-Ins charges a $6 vehicle fee. Dogs are allowed on leash. Best in spring (wildflowers) and fall (color); summer is hot but the Shut-Ins make it tolerable. No permit required.