Once you’ve seen Carlsbad Caverns in New Mexico, it’s hard to be impressed by many other cave systems. What Mammoth Cave has going for it is its sheer size (hence the name). It doesn’t boast much for underground rock formations and cool colored lights to illuminate them but does have over 390 miles of known passageways. The caverns are by far the longest discovered to date (South Dakota’s Jewel Cave comes in second around 150 miles).
The lack of cool stalactites and stalagmites is due to an upper sandstone caprock that prevents water from penetrating the the cave. Making things worse is that many of the few formations that were visible on our tour were sadly locked behind hideous metal fencing and bars to protect them from ignorant (and mischievous) tourists.
In the 19th century, the cave exchanged hands among private parties and at first was mined for calcium nitrate before it became an international tourism sensation. As a result, the formations suffered a lot of damage from souvenir hunters and profit seekers. It wasn’t until 1941 that the National Park Service took over and with the help of the newly formed National Speleological Society began active conservancy of the area.