The Easiest Way to Know More About Cave of the Mounds

Hello and welcome to Cave of the Mounds. Cave of the Mounds is named for its location here on the south slopes of the east Blue Mounds. The Blue Mounds are actually remnants of ancient mountains. The highest point in southern Wisconsin. 

So, do you think you can guess how old Cave of the Mounds is? If you’re thinking thousands of years, you may want to try adding a few more zeros.

That’s right! Cave of the Mounds is over a million years old. In a limestone rock, where the cave is formed is over 400 million years old. Which means the rock you’re about to walk through was around when the dinosaurs roamed here. Pretty cool, huh?

Well, over the next 10 minutes, you’re going to get a sneak peek at the journey you’re about to take through what has become known as Wisconsin’s oldest classroom. So, sit back, relax, and make sure you hold on because our first stop is a little journey back in time.

In 1828, Ebenezer Brigham made Blue Mounds, Wisconsin his home. This made him the first permanent settler in Southern Wisconsin. Ebenezer came to the state from Massachusetts to join Wisconsin’s lead run in the late 1820s. When Ebenezer set up a lead mine, he also built his own home. Which became a trading post, stagecoach stop, and eventually, Dane County’s first post office. Ebenezer lived a long life on this Brigham Farm never realizing that a greater discovery than lead lay just beneath his feet.

It was during a routine quarry blast on August 4th, 1939, that Cave of the Mounds was accidentally discovered. You see workers who were removing limestone from the quarry on the Brigham Farm that day had no idea they were blasting right above this huge underground cavern.

When the dust settled workers stared in amazement at the opening to this huge cavern.

“We were not allowed in at first because of the rubble” Shirley Martin, Daughter of Cave Developer Carl Brechler, “Although, we were allowed to come and just peek over all of the rubble. But eventually, when, as they started pulling the rubble out, we could get in further and further.”

Word spread quickly about this amazing discovery. Geologists advised the Brigham’s to seal the entrance until preparations could be made to protect this geologic treasure.

“To find something that you didn’t know was here before is really quite astonishing.” Jack Holzehueter, Historical Consultant, “We haven’t had that kind of experience in Wisconsin very much. New discoveries are really unusual.”

In May of 1940, Cave of the Mounds opened to the public. Since then, millions of people have seen the wonder you will see today.

“We knew that it was something that people would want to come and see and that it should be developed.” Fred Hanneman Jr., Son of Cave Developer Fred Hanneman.

“When it comes to natural phenomenon, I can’t think of another thing that has been discovered in Wisconsin since 1939 that begins to have this impact.” Jack Holzehueter, Historical Consultant.

By now you might be wondering how a cave forms. Well, to learn that, we’d have to take another trip back in time. But instead of human time, we’d need to go back in geologic time. Why? Because cave formation takes time. Lots and lots of time and H2O. Yep, water! 

If we went back in time 500 million years, you would be floating in a warm, shallow sea that covered most of North America. That sea was teeming with life. For example, the giant cephalopod is a distant ancestor of today’s squid. These creatures carried massive shells that were either straight or coiled. Cephalopods ruled the shallow waters prowling for smaller animals like the Trilobite. Trilobites made their homes scuttling across the sandy bottom. This giant arthropod, or bug, is Wisconsin’s State Fossil. These and a host of other creatures inhabited this ancient coral reef? Over time, the discarded shells of millions of these sea creatures built up layers and layers of limestone. That limestone is made up of the fossil remains of all those ancient sea creatures. If you look closely on your cave tour today, you might even see our giant cephalopod fossil. It’s more than 6 feet long.

So, that’s how the limestone rock formed. But how did this large hole form in the rock? Well, the simple explanation is this. Rainwater or melting snow combined with carbon dioxide to make an acid that trickled down through cracks in the limestone creating small cavities. Because of lead and other mineral deposits, deep underground, powerful sulfuric acid formed. This acid bubbled up through the rock enlarging the cavities further. Next, underground streams entered washing away sediments until finally, a large cavern formed.

Today you will see the geologic process continue. Year after year, day after day, water drips into the cave. Bringing with it dissolved crystals of limestone called “calcite”. As these tiny particles fuse together, they form intricate and varied shapes. These are speleothems. Slender, hollow stalactites hang from the ceiling while sturdy-looking stalagmites form statues on the floor. Speleothems come in many shapes and colors. It can take a long time. More than 100 years for a single formation to grow one centimeter (not an inch). Cave of the Mounds is one of Wisconsin’s most unique experiences. The cave is considered one of the most beautiful caves in the upper midwest. And is commonly referred to as the Jewel Boc of America’s Major Caves for its variety and delicacy of formations.

“If you were to describe an environment like what you have down here in this cave,” Richard Slaughter, Ph.D., Director of UW Madison Geology Museum, “ You know, you don’t realize that when you’re in here how weird it is. That the natural environment down here is total darkness. You know, and that the geology, you’ve got, there’s so much you can learn. You know, not just about the cave itself, but about how Wisconsin has changed over time.”

A tour of Cave of the Mounds is one of Wisconsin’s most unique and authentic experiences. In fact, the United States Department of the Interior and the National Parks Service have distinguished Cave of the Mounds as a National Natural Landmark because it is a treasure.

“It makes me realize that the world is filled with amazing things.” Richard Slaughter, Ph.D., Director of UW Madison Geology Museum, “And many of those things are closer than you think. And you might just, you know, there can be amazing things just around the corner a hundred feet away, a hundred feet below ground. You know, there are all sorts of surprises out there. You never know where, you know, as is the nature of surprises, you’re not sure where they are at or when they come up. They’re out there and this cave is one of them.”

Caver’s Motto:

Take nothing but pictures.

Leave nothing but footprints.

Kill nothing but time.

The Cave of the Mounds offers so much more than just a cave tour. While on these park grounds enjoy a picnic. Stroll through our prairie, savanna, butterfly, and rock gardens. Or hike our nature trails and witness the beauty of Southwest Wisconsin both above and below ground.

It is our responsibility to protect and conserve the cave and this fragile environment. 

So whether you’re a curious tourist or a budding cave enthusiast, today you’re going to be learning firsthand why Cave of the Mounds is truly a living underground adventure with a surprise around every corner.

Enjoy your tour!