In the 19th century, Kentucky's Mammoth Cave launched an entire, very competitive cave tourism industry in the area, In 1925, Floyd Collins was trapped in the cave system, which was the beginning of the end of the cave wars.
Research:

SYMHC Classics: Dr. Lucy Hobbs Taylor
29:58

Behind the Scenes Minis: Carry-on Bags
28:38

Gustave Flaubert and the ‘Madame Bovary’ Trial
45:15