On August 4th, 1939, a blast at the quarry sent 5,000 tons of rock into the air. The workers at the quarry blew the ceiling off of a cave. It was the only entrance and exit to this natural wonder. (For more information, read our article about the discovery of Cave of the Mounds)
When the cave was discovered, Charles Brigham Sr. called his geology department contacts at the University of Wisconsin in Madison to tell them what he’d discovered. He wanted to protect and preserve the cave on his property for science. In a time when many other caves shut down or were vandalized, Charles sealed up the entrance and protected it, whether himself or his son, by rifle. He did try to get the police to help him but to no success. His wife, Rosanna Gray, wrote in her diary on August 5th, 1939, “No police come so Charles Jr. takes his place in the car with his rifle! To tell people they cannot enter the cave.”