Great Onyx Cave, a show cave in Kentucky’s Mammoth Cave National Park, became known for its striking onyx formations and its role in the Flint Ridge cave region. Possibly discovered in 1915 by Edmund Turner and developed for tourism by landowner L. P. Edwards, it later figured in a 1929 court case over tours extending beneath neighboring property. Its owners refused to sell during federal land purchases in the 1930s, so when the park was established in 1941, the cave remained privately held until its sale to the National Park Service in January 1961. Geologically, it remains the only major Flint Ridge cave not connected to the Flint Ridge Cave System.