The brothers dynamited the opening to enlarge it and found the cave filled with calcite crystals that resembled sparkling jewels, hence the name the two bestowed on their find.
On Feb. 7, 1908, President Theodore Roosevelt declared the cave a national monument, one the National Park Service took over in 1933. The cave underwent further exploration over the years with people discovering miles of new passages.
The known length of Jewel Cave constantly changes as teams of cavers continue to explore it. In October of 2009, cavers found 850 more feet of passages, bringing the total length to 146.81 miles.
The temperature in Jewel Cave is 49 degrees F year round.
While nine species of bats live in Jewel Cave, they rarely venture more than a quarter of a mile into the cave.