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:

Elizabeth Peratrovich
43:42

SYMHC Classics: Dr. Lucy Hobbs Taylor
29:58

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