Missouri 21 — St. Francois Mountain Run

Missouri Route 21 threads 61 miles of genuine hill-and-hollow Ozark riding from MO-141 in suburban St. Louis County south toward the Arkansas border. The road earns its reputation through the St. Francois Mountains corridor — one of the oldest exposed mountain ranges in North America — passing Elephant Rock State Park near Belleview, skirting Taum Sauk Mountain (Missouri's high point, accessible via MO-CC spur), and crossing repeated ridgelines in Iron and Reynolds counties. The pavement is well-maintained two-lane with steady curves and minimal truck traffic; riders frequently link it with MO-32 east of Potosi and MO-8 for multi-county Ozark loops. The section south of Hillsboro toward Potosi is the technical core of the route.