Mammoth Cave National Park is a national park in the United States located in south-central Kentucky. It includes parts of Mammoth Cave, which is the longest known cave system in the world. The park covers 52,007 acres (21,046 hectares), mostly in Edmonson County, with small areas in Hart and Barren counties. The Green River flows through the park, and a smaller river called the Nolin River joins the Green River within the park.

The cave system was officially named the Mammoth–Flint Ridge Cave System in 1972 after a connection was found between Mammoth Cave and a longer cave system under Flint Ridge to the north. As of 2025, more than 426 miles (686 kilometers) of tunnels have been mapped in the system, more than 1.5 times longer than Mexico’s Sac Actun underwater cave system.

The park was created as a national park on July 1, 1941, following legal actions to take over land that caused much disagreement and still affect the region today. It was named a World Heritage Site on October 27, 1981; an international Biosphere Reserve on September 26, 1990; and an International Dark Sky Park on October 28, 2021.

Geology

Mammoth Cave formed about 330 million years ago in thick layers of Mississippian-aged limestone, along with some dolomite, siltstone, and shale. These layers are covered by a layer of sandstone, which has helped keep the cave system very stable. The types of sedimentary rock found in the area are usually found in places where the ocean once existed. Fossils found there show that Kentucky was once part of an ancient sea. The cave system includes more than 426 miles (686 km) of passageways. Each year, new discoveries and connections add several miles or kilometers to this total.

The top layer of sandstone is called the Big Clifty Sandstone. Thin layers of limestone within the sandstone create an epikarstic zone, where tiny underground tunnels are formed by the natural acidity of groundwater. This zone helps direct water flow to high-elevation springs, which appear at the edges of ridges. Water from these springs flows briefly on the surface before sinking underground again where the sandstone layer meets the limestone below. The human-explorable caves in the area formed in these deep limestone layers.

Below the Big Clifty Sandstone, the layers of limestone, from highest to lowest, are the Girkin Formation, the Ste. Genevieve Limestone, and the St. Louis Limestone. Water began reaching the Girkin Formation about 10 million years ago, and the upper parts of the cave formed around 3.2 million years ago. The large Main Cave passage on the Historic Tour is located at the bottom of the Girkin Formation and the top of the Ste. Genevieve Limestone.

Each major limestone layer is divided into smaller, named geological sections. Researchers study how these layers match the maps made by cave explorers. This helps create three-dimensional maps of the cave layers without needing to drill test holes or take rock samples.

The sandstone caprock is hard for water to pass through, except where there are vertical cracks. This protective layer makes many older, upper parts of the cave very dry, with no stalactites, stalagmites, or other water-formed cave features.

However, in some areas, the sandstone caprock has been dissolved and worn away, such as in the Frozen Niagara room. The boundary between limestone and sandstone can be seen by hiking from valley bottoms to ridges. As hikers reach the top of a ridge, the exposed rocks change from limestone to sandstone at a clear height.

In one valley in the southern part of the park, a large sinkhole called Cedar Sink has formed. A small river flows into one side of the sinkhole and disappears underground on the other side.

Visiting

The National Park Service provides several cave tours for visitors. Important parts of the cave, such as Grand Avenue, Frozen Niagara, and Fat Man's Misery, can be viewed on tours that last from one to six hours. Two tours use only lamps that visitors carry. These are popular choices instead of the electric-lit tours. Several "wild" tours explore areas outside the main parts of the cave, including muddy paths and dusty tunnels.

The Echo River Tour, one of the cave's most famous attractions, included a boat ride along an underground river. This tour was stopped because of problems with managing the tour and protecting the environment in the early 1990s.

Mammoth Cave headquarters and visitor center is located on Mammoth Cave Parkway. The park can be reached directly from I-65 at Exit 48. The parkway links to Kentucky Route 70 from the north and Kentucky Route 255 from the south within the park.

History

Human activity in Mammoth Cave dates back about 5,000 years. In the 19th and 20th centuries, remains of Native Americans were found in Mammoth Cave and nearby caves. Most of these remains were mummies, which showed that people intentionally buried them, following pre-Columbian funeral traditions.

An exception to this was found in 1935 when the remains of an adult male were discovered under a large boulder. The boulder had moved and settled on the man, who was a pre-Columbian miner. He had disturbed the rubble supporting the boulder. The remains were named "Lost John" and were displayed to the public until the 1970s. At that time, they were buried in a secret location in Mammoth Cave to protect them and due to growing concerns about displaying Native American remains publicly.

Research starting in the late 1950s by Patty Jo Watson of Washington University in St. Louis helped scientists learn more about the lives of the late Archaic and early Woodland peoples who explored caves in the region. The cave’s stable environment preserved evidence of their diets, allowing scientists to determine the age of the remains. Watson also developed methods to analyze the balance of plant and meat in their diets over thousands of years. This analysis showed a gradual shift from a hunter-gatherer lifestyle to one that included plant farming.

Another method used in research at Mammoth Cave is "experimental archaeology." In this process, modern explorers use the same tools and techniques as ancient people to understand the challenges they faced. This helps scientists learn how ancient people lived and worked in the cave.

Ancient remains and artifacts in the caves are protected by federal and state laws. When new artifacts are found, it is important to record their exact location. Moving even a small artifact can damage its value for research. Explorers are trained not to disturb evidence, and some parts of the cave are closed to the public unless the visit is for archaeological study.

In addition to human remains, other items like cane torches, drawings, gourd fragments, and woven grass moccasin slippers have been found in the Salts Cave section of the Mammoth Cave system in Flint Ridge.

The 31,000-acre (13,000 hectare) area known as the "Pollard Survey" was sold in 1791 by William Pollard. In 1796, Thomas Lang Jr., a British-American merchant, purchased 19,897 acres (8,052 hectares) of this land for £4,116.65. During the War of 1812, the land was claimed by a local county tax.

It is said that the first European to visit Mammoth Cave was either John Houchin or his brother Francis Houchin in 1797. While hunting, Houchin chased a wounded bear into the cave’s entrance near the Green River. Some family stories claim John Decatur "Johnny Dick" Houchin discovered the cave, but this is unlikely because Johnny Dick was only 10 years old in 1797. Francis Houchin, whose land was closer to the cave, is more likely the discoverer. Another possibility is Charles Houchin, a skilled hunter, but he was living in Illinois until 1801. Some sources suggest the cave was known before 1797, as other caves in the area were already known.

In 1798, the land containing the historic entrance to Mammoth Cave was surveyed and registered under the name of Valentine Simon. Simon used the cave to extract saltpeter, a key ingredient for gunpowder.

During the War of 1812, the saltpeter reserves in Mammoth Cave became valuable because of the Jefferson Embargo Act of 1807, which banned foreign trade. This shortage of saltpeter increased its price, making cave-based production more profitable.

In 1812, the cave was bought by Charles Wilkins and an investor named Hyman Gratz. The cave was mined for calcium nitrate on an industrial scale, using 70 enslaved workers to build equipment, haul soil, and process it. A half-interest in the cave was sold for $10,000 (worth over $150,000 in 2020). After the war, the cave was abandoned and later became a minor tourist attraction due to the discovery of a Native American mummy nearby.

After Wilkins died, his interest in the cave was sold to Gratz. In 1838, the cave was sold to Franklin Gorin, who wanted to use it as a tourist attraction. Gorin, a slave owner, used enslaved people as tour guides, including Stephen Bishop. Bishop, an African-American slave, made detailed maps of the cave and named many of its features.

In 1839, John Croghan of Louisville bought the Mammoth Cave Estate, including Bishop and other enslaved people. Croghan briefly operated a tuberculosis hospital in the cave in 1842–43, believing the cave’s air would help treat patients. Tuberculosis later caused Croghan’s death in 1849.

In 1866, the first photographs inside Mammoth Cave were taken by Charles Waldack.

Climate

The Köppen climate classification system shows that Mammoth Cave National Park has a Humid subtropical climate (Cfa). The United States Department of Agriculture identifies the Plant Hardiness zone at the Mammoth Cave National Park Visitor Center, which is located at an elevation of 722 feet (220 meters), as 6b. This zone has an average lowest temperature of -3.2 °F (-19.6 °C).

Biology and ecosystem

• A pair of Cave Crickets (Hadenoecus subterraneus) found on a Flint ridge.
• A millipede adapted to living in caves found in Mammoth Cave.
• An individual of the species Palaemonias ganteri, also known as the Kentucky cave shrimp. This species is found only in this cave system.
• A Cave Crayfish (Orconectes pellucidus).
• Eurycea lucifuga, also known as the Spotted-tail salamander. Unlike other cave salamanders, such as the olm, this species has working eyes and skin color.
• Amblyopsis spelaea (the northern cavefish) is a blind species of cave fish.

The following bat species live in the caverns: Indiana bat (Myotis sodalis), gray bat (Myotis grisescens), little brown bat (Myotis lucifugus), big brown bat (Eptesicus fuscus), and tricolored bat (Perimyotis subflavus).

Together, these and other rare bat species, such as the eastern small-footed bat, had populations of about 9 to 12 million in the Historic Section. While these species still exist in Mammoth Cave, their numbers are now fewer than a few thousand. Restoring this part of Mammoth Cave and helping bats return is an ongoing effort. Not all bat species live in the cave; the red bat (Lasiurus borealis) lives in forests and only enters caves rarely.

Other animals that live in the caves include: three species of cave crickets (Hadenoecus subterraneus, Ceuthophilus stygius, and Ceuthophilus latens), a cave beetle (Pseudanophthalmus inexpectatus), several types of fishing spiders (Dolomedes spp.), a cave salamander (Eurycea lucifuga), two species of eyeless cavefish (Typhlichthys subterraneus and Amblyopsis spelaea), a cave crayfish (Orconectes pellucidus), and the Kentucky cave shrimp (Palaemonias ganteri). Some surface animals may hide near the cave entrances but do not usually go deep into the caves.

The section of the Green River that flows through the park is officially named "Kentucky Wild River" by the state government through the Office of Kentucky Nature Preserves' Wild Rivers Program.

According to the A. W. Kuchler U.S. Potential Natural Vegetation Types, Mammoth Cave National Park has an Oak and Hickory (100) potential vegetation type with an Eastern Hardwood Temperate Broadleaf and Mixed Forest (25) potential vegetation form.

Common fossils found in the cave include crinoids, blastoids, and gastropods. The Mississippian limestone has revealed fossils of more than a dozen shark species. In 2020, scientists found part of a Saivodus striatus, a shark species similar in size to a modern great white shark. The fossil shark species Glikmanius careforum and Troglocladodus trimblei are found only in this cave.

• Jaw cartilage of Saivodus striatus found in Mammoth Cave
• Fossilized braincase of a cartilaginous fish found in Mammoth Cave
• Fossilized tooth of Troglocladodus trimblei, found only in the limestones of Mammoth Cave
• Tooth-plate of a shark-like petalodont fish
• Dorsal fin spine of a ctenacanth shark, exposed from the limestone of Mammoth Cave

Name

The name of the cave means the wide and long passages that lead to the Rotunda near the entrance. People used this name a long time ago, before the large cave system was better explored and mapped, showing many long tunnels. No fossils of the woolly mammoth have ever been found in Mammoth Cave. The cave's name is not related to this extinct animal.

Cultural references

• A large part of the work by American poet Donald Finkel was inspired by his time exploring Mammoth Cave National Park. Examples include the poem "Answer Back," written in 1968, and the book "Going Under," published in 1978.
• The design of one of the first computer games, Will Crowther's 1976 "Colossal Cave Adventure," was partly based on the Mammoth Cave system.
• The video game "Kentucky Route Zero" includes a standalone expansion called "Here and There Along the Echo," which is set between its third and fourth acts. This expansion features a fictional hotline that provides information about the Echo River for travelers. The game's third act also takes place partially inside the Mammoth Cave system and includes references to "Colossal Cave Adventure."
• H. P. Lovecraft's 1905 short story "The Beast in the Cave" (published in 1918) is set in "the Mammoth Cave."
• The American rock band Guided by Voices mentioned Mammoth Cave in their 1990 song "Mammoth Cave" from the album Same Place the Fly Got Smashed.
• In chapter 75 of Herman Melville's 1851 novel Moby-Dick, the "Kentucky Mammoth Cave" is used as a metaphor to describe a sperm whale's stomach.
• In 1858, fiction writer Lillie Devereux Blake wrote a fictional story for The Knickerbocker magazine about a woman named Melissa who abandoned her tutor in Mammoth Cave. The story claims Melissa returned to the cave fifteen years later to end her life. Researcher Joe Nickell explained in Skeptical Inquirer magazine that people who believe in ghosts sometimes claim to hear Melissa weeping and calling for her tutor. Nickell noted that caves often produce sounds that the brain may interpret as words or weeping, a phenomenon called pareidolia. Blake visited Mammoth Cave with her husband, Frank Umsted, traveling by train, steamer, and stagecoach.
• The rock band Black Stone Cherry mentioned Mammoth Cave in their 2008 song "Ghost of Floyd Collins."