Maryland Department of Natural Resources

Caves in Maryland

 Taking a break (photo by Dennis Slifer)
Taking a break

Take a virtual tour of 18 Maryland caves by browsing to A Gallery of Maryland caves

While not as numerous or spectacular as caverns in Kentucky, Tennessee, or the Virginias, Maryland's caves are interesting and valuable resources. Caves are important habitats for a variety of plants and animals, some of which are endangered. Caves are often an integral part of the natural drainage system which collects and purifies ground water. Other caves are the source of drinking water for communities. As cultural resources, many Maryland caves have long and interesting histories. They have served as shelters for prehistoric populations, sources of minerals for commerce, and even as cold storage for dairy products. Some caverns contain fossils remains of ancient sea creatures and Ice Age mammals. For a detailed study of Maryland caves, see Educational Series Report 3: Caves of Maryland.

One Maryland cave, Crystal Grottoes in Boonesboro (Washington County), is open to the public. Crystal Grottoes is about an hour drive from Baltimore and Washington D.C. It is well worth the pleasant drive, and there are many other interesting places to see in the vicinity including Antietam Battlefield, Harpers Ferry and Washington Monument State Park. Crystal Grottoes is located at 19821 Shepherdstown Pike, Boonesboro (301 432-6336). For more information on Crystal Grottoes see the Crystal Grottoes page.

Map showing location of Maryland caves.
Map showing location of Maryland caves.
Karst terrane and its relationship to caverns (adapted 
					from USGS)
Karst terrane and its relationship to caverns (adapted from USGS)

At least 53 caves occur in Maryland. Most of these are located in western Maryland, in Washington, Allegany, Garrett and Frederick Counties. There are no known caves on the Eastern Shore or southern Maryland. The reason for this uneven distribution is due primarily to two geologic factors: bedrock type and drainage. Caves usually form when ground water slowly dissolves slightly soluble minerals in limestone and marble. The water flows through the rock because gravity forces it along cracks, called joints, in the rock. The limestone minerals, mostly calcite and dolomite, dissolve in slightly acidic water. Rain water is naturally slightly acid because it absorbs atmospheric carbon dioxide to make a very dilute solution of carbonic acid. When rain water passes through soil, it can become even more acidic by absorbing more carbon dioxide and other organically-derived acids. This acidic water then filters down to the limestone bedrock where it flows through pores and joints. Over thousands of years, this process enlarges the voids and spaces in the limestone, forming caves. Maryland's caves occur mostly in limestone and marble. Exposures of these rocks are limited to the central and western parts of the state. Therefore, most of Maryland's caves are found in those regions. These caves are probably less than 10 million years old

A tight squeeze (photo by Dennis Slifer)
A tight squeeze

The landscape that develops over limestone and marble regions is often shaped by the same geochemical process that forms caves. Sinking streams, sinkholes, and springs are often found in areas underlain by limestone. This type of topography is called karst. While visually interesting, karst topography can be a potential hazard. Sinkholes can develop unexpectedly and rapidly, swallowing up cars, houses and whole towns. For more information on karst and karst terrane hazards, see MGS Factsheet 11: Foundation Engineering Problems and Hazards in Karst Terranes.

Small Sinkholes (photo by Dennis Slifer)
Small Sinkholes

The mild temperatures and high humidities found in most Maryland caves are relatively constant throughout the year. This kind of environment makes caverns an ideal habitat for many animals. A variety of spiders, insects, amphibians, reptiles, fish and mammals make caves their seasonal or permanent homes. Salamanders, wood rats and several types of bats are particularly attracted to caves. These animals currently suffer from loss of habitat in Maryland due to development. Caves offer refuge to these creatures when forests and farmland are destroyed and surface streams are diverted and polluted. Other animals including cave crickets and cave moths live primarily in the subterranean world. In the past, aboriginal human populations used caves for shelter and religious ceremonies. More recently, some of these caves have been mined as a source of metal ores, and nitrates for gunpowder. Maryland caves have a rich natural and cultural history that requires careful preservation and study.


Spelunking, the sport of cave exploring, is a popular hobby. For information about caving, see the links below. Do not explore caves unless you know what you are doing, and never enter a cave alone. Make sure you are accompanied by an experienced caver and you are outfitted properly. Many caves require rope work and rappelling skills, and explorers need to be in good physical condition. Always ask permission from the cave owner to enter a cave . Almost all Maryland caves are on private or restricted property. Some caves are expressly closed to exploration. Remove nothing from a cave. Failure to follow these rules can result in injury, arrest and prosecution, and death. For instance, there have been several reports of bad air in at least one Maryland cave;. Only an experienced caver, with specific knowledge of this cave would recognize the risk of entering this cave. For more information about caves, see MGS's reissued Educational Series Report 3: Caves of Maryland, and our list of caving resources.

A Note on White Nose Syndrome and Bats : Please be aware of the spreading disease wiping out bat populations in the east.  For information on this problem see the DNR page Bats and Diseases.

Cavers should check in advance this updated list of closed caves from the National Speleological Society.