It was on Sept. 1, 1885, that Walter J. Mercer would, just by chance, make a discovery that would forever change his life. After spending most of that hot summer day having no luck prospecting for gold, Walter discovered a subterranean wonderland that is known today as Mercer Caverns.
Beginning on Sept. 2, 1885, and continuing for the next two weeks, Walter, accompanied by his friend Emile K. Stevenot, a mining geologist/assayer from Carson Hill, and E.F. Floyd, the Murphys schoolmaster, explored the caverns.
During this early exploration of the caverns the skeletal remains of six people--four adults, one child and one infant--were found. After extensive examination and study of the bones by the Harvard Museum of Comparative Zoology, the University of California and, in later years, the Smithsonian Institute, it was determined that the remains belonged to members of the Mi-Wuk tribe of native Americans who lived in the area some 1500 to 2000 years ago.
The original name of the caverns, New Calaveras Cave, can be traced back to the human remains found by the early explorers. "New Calaveras" means "New Place of Skulls". In the years that followed the name of the caverns was changed to Mercer's Cave and in 1946 became known as Mercer Caverns.
In addition to the human remains found in the caverns, lower down in the caverns the explorers found skeletal remains of what at that time was believed to be a prehistoric bear encased in flowstone. In 1899, the Smithsonian Institute determined that the remains of the animal first thought to be a prehistoric bear were actually the remains of an extinct Sierra Ground Sloth, megalonyx sierrensis. The creature was a grazer in the grassy forests of the Sierra Nevada during the last ice age and was similar in size to a contemporary Giant Anteater, approximately up to 7 feet long and weighing up to 140 lbs.
After the initial exploration of the caverns, Emile Stevenot proposed that the formation now known as the "Cave Twins" be used as touching stones so that visitors would be able to actually touch and feel a cave formation and also so that visitors would not be tempted to touch other fragile and delicate formations in the caverns.
The Sept. 12, 1885, headlines in the Calaveras Weekly Citizen announced the discovery of the New Calaveras Cave: "The town of Murphys has been considerably agitated by the discovery of an immense cave near that place. The cave was discovered by Walter Mercer a couple of weeks ago. It is situated about a mile from Murphys near the road from that place to Sheep Ranch. The cave has only been partially explored, but enough has already been discovered to justify us in saying that it will prove a major attraction to tourists and curiousity seekers. The cave is in a limestone region, as in fact are all of the great caves of the world. Some of the apartments are of immense dimensions. It has been explored to the extent of seven or eight hundred feet."
The first known commercial tour of the caverns was held about the same time. Guests were charged 50 cents for the tour which lasted about two hours. They used candle boards called "glims" which held six mining candles to illuminate their way. The first visitors toured the caverns by way of some fixed ropes and ladders and only went through about 930 feet of the cave. When the visitors used the ropes they held the candle board, with lighted candles, in their teeth, always careful of the flames and the hot wax dripping from the candles.
The glims soon gave way to torches, coal oil lanterns, household kerosene lanterns and then railroad lanterns. Hand-carried light sources were eventually replaced with one of the first electrical lighting systems installed in a western commercial cave. The first electrical lighting system was installed in 1901. Tinted glass was placed in front of the original electric lights to give the cave color. Colored lights were used for many years but over time were replaced by regular tungsten bulbs and currently fluorescent and LED bulbs.
On Sept. 15, 1885, California state mineralogist Henry G. Hanks spent the entire day exploring the caverns. Afterwards he announced that the cave was formed when an ancient earthquake caused the roof to collapse into a huge void. It is currently believed that Mercer Caverns was formed in a large lens of recrystallized limestone in the Calaveras Group, a jumble of miscellaneous slivers of rock found in the Sierra Nevada. It is believed that the caverns began forming in the mid-Miocene Epoch approximately 12 million years ago during the Tertiary Period of the Cenozoic Era as acidic ground waters filtered into the cracks of the limestone and began dissolving it. For more about the geology of the cave, see our Geology page.
Shortly after the cave was discovered Walter built a house near the cave entrance. In later years admission tickets and gifts were sold out of the building which still stands today. Soon after building his house Walter began to install stairs to make the journey into the caverns easier on visitors.
In 1888, at the age of 34, Walter was working on an exit in the caverns when his rope broke and he fell approximately 30 feet. The fall caused him serious neck and back injuries and is believed to have led to Walter's development of tuberculosis of the spine years later. It was the injuries that Walter suffered in the fall together with many years of crawling through the damp cave climate that have been blamed for his death at an early age.
On November 1,1900 Walter J. Mercer died at the age of 46 of spinal meningitis. An article in the Calaveras Prospect dated November 3, 1900 stated "Walter Mercer, discoverer and proprietor of the famous Mercer's cave, of Murphys, died Thursday night in Stockton after a long and serious illness." After Walter died his wife Margarita (Margaret) Mercer continued to operate the caverns. Mrs. Mercer eventually turned the operation of the caverns over to her daughter Eva Mercer Stephens who with her husband Milton Stephens continued to operate the cave until Milton's death in 1946. The Mercer family operated the cave for 61 years.
After the death of Milton Stephens in 1946, the caverns were sold to Sterling and Vivian Carter. Mr. Carter renamed the cave Mercer Caverns and operated the caverns until April 23, 1965, when it was sold to two businessmen, Burke Malcolm and Bruce Prather. Shortly after purchasing the cave Mr. Carter, with the help of PG&E illumination specialists, installed what was at that time a state of the art cave lighting system consisting of 48 floodlights equipped with color filters.
On August 2, 1985, as part of the centennial celebration of its discovery, Mercer Caverns was designated as a Point of Historical Interest, No. 004, by the State of California. A plaque at the entrance to the caverns commemorates this honor.
On Sept. 1, 1985, Mercer Caverns celebrated the 100th anniversary of its discovery by Walter J. Mercer.
Between October and November 1985, Bruce Rogers, USGS, Charmaine Legge, and Paul Decker, all of the Golden Gate Grotto of the National Speleological Society, mapped the caverns for the very first time in its 100 year modern history. Congratulations goes out to this trio of cavers who produced the first known map of Mercer Caverns. A copy of the map of the caverns drawn by Bruce Rogers is on display at the Caverns and can also be viewed here.
On Sept. 1, 2010, Mercer Caverns celebrated the 125th anniversary of its discovery by Walter J. Mercer.