On August 4th, 1939 just 25 miles from Madison, Wisconsin, Lance Dodge was contracted by Brigham farms to perform a quarry excavation. During his drilling, he suspected that there may have been a cavity below due to his drill bit falling 30 feet more than expected. When he set off his blast at 11:00 AM, the Cave of the Mounds entrance was discovered.

400 million years ago during the Ordovician Period, shallow and warm seas covered this part of Wisconsin. As currents passed through areas of the cave, many species of sea life were able to thrive among its’ cavities. Millions of years later as the seas started to recede from the cave, erosion began to take place. What we are now left with is fossilized sea life and layers of calcium carbonate shell debris that have accumulated, causing them to slowly hardened into the limestone, known as Galena dolomite, that fills the cave we can explore today.