Cavern History

People & The Cavern 

Early Native Americans

Thousands of years ago, the first inhabitants of North America were just making their way into the continent. A common belief is that they came over the “land bridge” from what is now Russia to Alaska and migrated south. In their travels, some of them passed by the entrance to the cavern and may have even lived nearby. A chert outcrop lies near Moaning Cavern (when heated, chert hardens to a material that can be chipped into sharp-edged flakes for excellent arrowheads and other points for tools).  It appears to have been quarried many years ago for its hard rock. Near the outcrop, fired bits of chert and partial points have been found. The large size of the quarry may mean the first humans to live around the cavern arrived thousands of years ago.

Other evidence of early human residence is skeletal remains. Some of the human bones found in the cavern have been estimated to be at least 12,000 years old, based on the thickness of the calcite layers found on the bones and the results of carbon and uranium-thorium dating techniques.

Anthropologists dug a trench in an area of the main room in 1952 and removed a number of fragmented human bones from an area of mud that had been covered by layers of dripstone. Many of these bones had layered films of calcite covering them. Calcite layering builds in thin layers, similar to the growth rings of trees. The extensive amount of time it takes for the deposits to build up gives evidence as to the age of the bones. 

There is no evidence these early residents explored the cave voluntarily. No remnants of pine or reed torches or ladders of any kind have been found in or near the cavern. The more likely explanation for the presence of the bones in the cavern is that they resulted from accidents. The entrance may have been hidden by plants. The shape of the cavern made it easy to slip into and impossible to get out of without ropes or ladders.

Most of the bones found in the cave were shattered and dispersed. Very few complete skeletons of these ancient people have been recovered, but those parts recovered indicate these humans were not the ancestors of the MiWok who were living in this area when white settlers arrived. 

Some of the artifacts that were found among the bones also help with dating, as well as give us some insight into these ancient people. The age of the bracelet displayed at the visitor center has been dated within the past 500 years. It is made of sea-snail shells and suggests regular trading with other people over a wide region. The mother-of-pearl necklace was found in the clay layer and estimated to be over 8,000 years of age.

Gold Miners

Miners invaded this area in large numbers during the late 1840’s. In their search for gold, they explored the cavern to a great extent. They entered through the small natural entrance and then lowered themselves to the floor of the main room by means of a large ore bucket on a winch. They used candles and whale oil lamps for light. In their explorations, they did not find the riches in gold they sought, but a mound of skeletons instead.

J.B. Trask wrote the first account of Moaning Cavern in the Daily Alta California on December 7, 1851.  Trask described his descent and exploration of the cavern. He found four rooms: the “main room,” a second room below it about 100 feet, and two other rooms. Trask claimed he found several human skeletons in the second lower room.


In 1920, some local residents purchased the cave property by way of a logging claim. Members of this group explored the cavern and decided to open it for tours.

The new owners dynamited the diagonal entrance to make it wide enough for a person to pass through. In 1921, wooden stairs were then built in this new passage a total of 65 feet down to the top of the main chamber. At this point, a winch was used for lowering people and supplies to the floor one hundred feet below. In 1922, the spiral staircase was built and the cavern was then opened to the public.

After the cavern was opened, the owners discovered a number of human bones in the floor and under calcite growths in the main room. Many bone fragments were dug up and removed from the main room. The partial human skull, the collection of various human bones, and the artifacts on display in the visitor center came from this excavation.

The first Moaning Cavern visitor center was built in 1924. Ownership of the cavern has changed several times over the years. The visitor center has been rebuilt and expanded, and other attractions have been added.



The Stairs

When the cavern was being developed for tourism, the owners needed a way to get people down the remaining 100 feet past the platform at 65 feet below surface that was reached by the wooden stairs. The original plan was a very large structure that would take up a lot of space in the middle of the main chamber. It would have completely blocked the view of the room from the first platform. Not only would it be an eyesore, the construction of it could have caused irreversible damage to the cavern. Luckily, a friend of the owners had the knowledge and expertise in a fairly new field that would save the day. In 1922, Albert Tangeman built the spiral staircase using scrap metal from an old WWI battleship. This feat of architectural wonder is amazing in how it was built. While arc welding was not brand new, it had never been used as the sole support for a structure. The 100-foot spiral staircase in Moaning Cavern does not have a single nut or bolt helping to hold it together. Every last joint was joined together using arc-welding. It was one of the first major structures to ever be built using only this method.

The finished structure had 144 stairs and spirals around 7½ times. It has given hundreds of thousands of visitors the privilege of descending into the largest cave chamber in California.

There was, however, one bad side-effect from the construction of the staircase. For many years after it was built, the moaning sounds completely stopped. It was believed the widening of the diagonal passage and the insertion of the stairs changed the airflow into the cavern, stopping the moaning sound (this was when it was still believed that blowing air caused the sound). In the mid-1970’s, after extensive research, the new owners of the cavern found the holes below the draperies. However, what they found were holes filled with debris from the staircase construction. Not knowing their significance, the builders had used the holes as handy trash holders! The holes were cleared and, with a little experimenting, the source of the moan was found and restored.  



What’s in a name?

Before the cavern was developed for visitors, it occasionally emitted a “moaning” sound. This sound was apparently loud enough to be heard on the surface. The MiWok Indians who lived in the area had a legend about the spooky sound emanating from the cavern entrance. They said there was a stone giant named Yayalli who lived in the cave and lured people to their deaths. Not only did this legend make a handy explanation of the sound, it also helped to prevent many potential accidents. Some people of this century theorized that it must be the wind blowing across the cavern entrances (like blowing over a bottle opening) or blowing through the cavern. To this day, that is the most common misconception. 

The true source of the mysterious sound comes as a surprise to all. The moaning sound is actually a somewhat recent development in the cave as far as the cave’s history goes. It wasn’t until after the cave had been formed and the calcite formations had been growing for some time that the moan actually started. As the cavern formations grew over the centuries, getting bigger and more elaborate, a certain area took on an interesting characteristic. There is a section of the cave wall that comes to an abrupt end, forming an overhang about halfway into the main chamber. As calcite deposits continued to run down this wall and drop off the edge to the floor below, the calcite deposits eventually formed a set of beautiful draperies hanging off the overhang and a large mound where the water drops landed on the floor. This is all part of normal cave growth. However, an interesting circumstance changed this normal process. The amount of water flowing into this area of the cave became so excessive that when the water dropped to the floor, instead of depositing more calcite, it actually started to erode the rock. Over hundreds of years several holes have been “drilled” into the rock. These holes are similar to bottles where they have a long, narrow neck and a wide bottom. During certain times of the year, when the water level in these holes is low enough and a water drop lands in one, it produces a hollow thumping sound. Due to the amazing acoustics of the cavern, this sound is amplified to the point that it has a sound similar to a low moan when it reaches the surface. Unfortunately, the natural occurrence of this sound is rare. If the conditions are right, a cavern naturalist may be able to drain the water out of a hole in the hopes of a water drop hitting just right. Even then, the sound no longer reaches the surface. It is thought that the addition of the spiral staircase and the visitor center covering the openings have affected the acoustics.     



Moaning Caverns Today

Today Moaning Caverns includes a nature gift shop, gem mining and gold panning operation, a developed nature trail and picnic areas. Two different tours are offered into the cavern. Both tours are available year-round.

The Spiral Tour is our most popular tour. It enters the cavern by the wooden stairs leading to the first landing 65 feet (19.8 meters) below the surface, then descends the 100 feet (30.5 meters) of the spiral staircase to the floor of the main chamber and returns the same route. 

The Expedition Tour  Visitors will explore the undeveloped passages deep within the cavern for about 2 hours and it is an experience you will remember for the rest of your life. There are no lights, stairs, or walkways. Instead, visitors daringly explore by climbing and belly crawling with lighted helmets to show the way! Visitors are guided, crawling and climbing, through a maze of tight passages and small rooms that twist and turn under the main room. Hard hats are supplied. These hats have mounted lights, so the caver can see and have their hands free.