Inner Space Cavern was established as a for-profit tourist attraction in 1966. The cave was discovered three years prior when the Texas Highway Department was drilling core samples to ensure that the ground at this location was sturdy enough to support an overpass embankment for IH 35. After drilling through 33.5 feet of mostly solid rock, their drill bit fell through the roof of what is now known as the Discovery Room. The first person to enter the cave was a Mr. Jack Bigham, followed closely by the Highway Department geologist, Mr. Jim Sansom. See "Discovery of Inner Space Cavern" for Mr. Sansom’s humorous account of the discovery of Inner Space.
There were five entrances to the cave in recent history. On the tour, we refer to these as ‘Bone Sinks;’ sink holes that we found bones in. When a room of the cave became so large that the roof was no longer strong enough to support its own weight, it would collapse. This allowed animals to enter the cave. We found fossils of at least 44 different species of animal, 11 of which are now extinct. For more detailed information on the geological and paleontological discoveries of the cave, please reference the technical paper written by Mr. James Sansom and Dr. Ernest Lundelius entitled Inner Space Cave: Discovery and geological and paleontological investigations.
Reverend William W. Laubach owned the land that the Texas Highway Department was drilling into when they discovered the cave, and therefore owns the cave as well. He asked permission from the Highway Department to commercially open what is now known as Inner Space Cavern. The Highway Department agreed, it was concluded that the 33.5 feet of limestone between the cave and the surface was enough to hold the approach embankment for the overpass, and construction was resumed as planned. It took three years for the Georgetown Corporation (the business side of Inner Space) to dig out the entrance, lay the pathways, and put in the lights along the trail. Inner Space opened to its first customers in June 1966.