Fisher Ridge Cave System in Kentucky, near Mammoth Cave National Park, is a vast cave network mapped to 130.001 miles by November 2019, ranking fifth-longest in the United States. People first entered it thousands of years ago, when Archaic Native Americans left footprints, torch charcoal, and markings deep inside. Its modern rediscovery came in January 1981, when Michigan cavers opened the Historic entrance and soon mapped nearly 10 miles. Later exploration revealed immense dry tunnels, active underground rivers, canyon passages, and remote sections requiring base camps. Although some surveyed passages lie very close to Mammoth Cave, no proven connection has ever been found.