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:

Behind the Scenes Minis: Whoopsy Whimsy
24:41

Great Lisbon Earthquake of 1755
39:02

Benzedrine, Pervitin, and WWII
39:42