List of caves of Maryland

The subject of this article and a reference book of the same name, Caves of Maryland was first released by the Maryland Geological Survey (MGS) in 1950. Information about Maryland caves was first gathered into a series of reports by Martin Muma in the mid-1940s, working under the MGS. After the release of these articles in 1946, a more comprehensive study was begun by William Davies, whose years of fieldwork led to the compilation of the premiere edition of Caves of Maryland in 1950.[1] Since its publication, this reference work has remained the principal source for information about Maryland caves, and has served as an outline for the work to follow.


Following the release of the first edition of Caves of Maryland in 1950, several other attempts by various parties and interested groups have been made at expanding available information concerning Maryland's subterrain. In the late 1960s the MGS sponsored another statewide survey, undertaken by Richard Franz and Dennis Slifer, and a second, expanded edition of Caves of Maryland was released in 1971. It was not until the inception of this second project that areas west of Washington County were even thoroughly canvassed; even after the conclusion of the Franz/Slifer survey, it was speculated that even more, undiscovered caves could still remain in more remote portions of the western counties, prompting the need for an additional version, but since that time there have been no additional state sponsored reports or surveys released to the public.

In Maryland, a cave is defined as any subterranean cavity large enough for a human to enter.[2] This definition has led the authors to include several shelter caves, fissures, and mines that in states with larger, more complex cave systems, might otherwise go unlisted.


Cave locations are typically well-guarded secrets, as property owners are most-often fearful of liability issues and damage to their lands. Likewise, experienced spelunkers are also wary to guide novices to cave locations, fearing they might recklessly endanger the natural balance of these sanctuaries, making them inaccessible to all. While most find cave vandalism unimaginable, there are some who, whether out of carelessness, malice, or ignorance, have hopelessly destroyed beautiful caves forever. For this reason, precise locations of caves are seldom published. Rather than using a coordinate system, the MGS' "Caves of Maryland" provides approximate locations using a quadrangle system to be employed with the use of 7.5-minute topographic maps. Neither coordinates nor quadrangular data are posted on this page at present, only surrounding terrain and the condition/accessibility of said caves when known. While limited data and pictures about Maryland's caves can be found on the MGS’s website, the best sources of information are local speleological grottos and knowledgeable enthusiasts. To learn more about the caves of Maryland, their locations, and ethical caving practices in general, contact the Tri-state Grotto or Western Maryland Grotto, an internal organization of the National Speleological Society.

Maryland geology and caves

Most of Maryland's caves occur in its three westernmost counties (Washington, Allegany, and Garrett). While Maryland may be smaller than many of its neighboring states containing larger numbers of caves, its geology likewise allows for the formation of underground cavities, most of which are hollowed out by chemical processes—these caves are known as solutional caves. Non-solutional caves are carved out by weathering and are typically of smaller size and of little interest to spelunkers. Underlying layers of carbonate rocks form much of Maryland's bedrock; precipitation and groundwater react with such rocks as dolomite, limestone, and marble, dissolving the rock and forming small fissures and chambers that allow for the entry of more water and the dissolution of more of the carbonic rock. Being able to identify the different types of rock that caves are likely to form in can provide a great deal of background into a cave's likely history, and thus these rock formations will be further discussed moving east to west across the state.

Coastal Plain – this is the area of Maryland extending from just west of the Chesapeake Bay to the Atlantic Ocean: Precambrian rocks are mostly overlain by gravel, silts, marls, and sands, and consequently no solutional caves are known to exist in this region of Maryland.

Piedmont Plateau – an area of gently rolling hills and flatlands, the Piedmont is home to only a few of Maryland's caves, as most of its members are unsuitable for their development or are largely hidden from view beneath surface settlement. Exceptions in the uplands area include the Wakefield and Cockeystown marbles, which are known to include but a few caves. In the lowlands portion of the Piedmont (known as the Frederick Valley) caves are found in the Frederick Formation and Grove Limestone (upper Cambrian and lower Ordovician, respectively); while several other limestone members exist (Tomstown and New Oxford), no caves have been located within these members.

Blue Ridge & the Great Valley – the Blue Ridge rises up from the Piedmont just west of Frederick in the first of its two mountains, Braddock/Catoctin. Here older limestone and dolomites from the Cambrian/Ordovician make an appearance, offering up a few caves in the Frederick/Middletown Valley vicinity. On top of these, older, harder thrust sheets of metamorphic rocks from the Paleozoic give these mountains their well-defined crests and ridges. Wolf Rock, home to Maryland's best-known non-solutional cave, is an example of quartzite that has endured while Catoctin Mountain has weathered around it.

South Mountain, which serves as a natural border between Frederick and Washington counties, is the western edge of Maryland's Blue Ridge, giving way to an area of relatively little relief, known as the Great (or locally, Hagerstown/Cumberland) Valley. Here the harder metamorphosed rocks of the Blue Ridge are replaced by carbonates, sandstones, and shale that grow progressively younger moving west, entering the early Ordovician period. The highest concentration of Maryland caves lies within the Hagerstown Valley, where well-established waterways have cut into the underlying carbonate rocks.[3] Recent fieldwork, combined with the observations of Franz and Slifer, indicate that the most cavernous units exposed in the Great Valley are, from oldest to youngest, the Tomstown Dolomite, the Cavetown member of the Waynesboro Formation, the lower beds of the Elbrook Formation, the Rockdale Run Formation, and, especially cavernous, the Chambersburg Formation. The probability of cave development, however, is also very strongly influenced by the presence of structural features such as anticlinal axes, synclinal troughs, and faults. In contrast to the larger caves of neighboring West Virginia, caves in the Great Valley are generally quite shallow with little internal relief. In-cave relief rarely exceeds 50 feet (15 m) in Washington County. High deformation and faulting allows surface waters to penetrate rock vertically and reach the shallow underlying water table quickly without much lateral travel. This serves to limit cavern development considerably, and of the many caves in Washington County, only Crystal Grottoes is known to exceed 1,000 feet (300 m) in length, and it attains such length from having a maze pattern of passages, rather than a long continuous stream conduit.

Ridge & Valley Region – is the name of the physiological province extending west of the Great Valley to the western portion of Allegany County. This region is traditionally defined as starting at Fairview Mountain and is characterized by repeating southwest- to northeast-trending ridges and valleys. A thrust fault just east of Fairview indicates where younger rocks from the Ordovician through Devonian were overthrust by their Cambrian neighbors to the east. The region is built upon shale and sandstone from the upper Ordovician and lower Silurian periods, with little or no cave-bearing limestone seen until the lower Helderberg Group, Wills Creek Formation and Tonoloway Formation. Thicker formations of the upper Devonian consist of the Keyser Formation and New Creek Limestone, in which some of the largest caves in the state can be found.

Allegany Plateau – the Allegany is a rolling upland punctuated by deep, rounded valleys and ridges of distinct, broad anticlines. Shale and sandstone of the Ordovician and lower Silurian are replaced by limestone formations which continue into the lower Devonian. These younger rocks have settled to a depth equal to that of the much older rocks of the Ordovician; this change in depth occurs along a fault just east of Dans Mountain. Moving west from outcrops of early Devonian limestone, the Helderbergian limestones pinch out and the formation consists of clastic rocks that bear no caves. Synclines within this region have preserved remains from the younger Carboniferous Period—the period containing Maryland's only natural source of carbon fuels—within the Mississippian system lies the Greenbrier Formation, the next oldest limestone member known to contain caves. The Greenbrier is relatively thin but contains eight known large caves, including the largest cave in Maryland, Tanglefoot Cave. The youngest rocks to contain caves are in Garrett County: they are Pennsylvanian in age. All younger sediments have been removed from the landscape with the exception of the Dunkard Group, a small knob in Allegany County that is Permian in age.

List of caves

All caves given in the 1976 republication of Caves of Maryland will be listed below by county. The condition and status of many of these caves are unknown at this time; in an effort to establish an up-to-date record of these caves, editing of the list with any new information is encouraged!

Allegany County

After Washington County, Allegany County contains the second-highest concentration of caves in Maryland. The many ridges of the Appalachians' Ridge & Valley Province provide terrain well-suited to the formation of caves. While rocks here vary in age from Silurian to Mississippian, most caves are developed in the middle of this range in the Tonoloway and Helderberg formations. Like Washington County, distribution of caves within Allegany County often tend to run in patterns that parallel folds in local mountain chains.

Baltimore County

Formation of caves and sinkholes in Baltimore County is found within its Piedmont marble: the Cockeysville and throughout the limestone valleys. Note that there are also caves and sinkholes throughout the limestone valleys of Greenspring and Long Green. There are likely in excess of 20 caves of varying size in Baltimore County.

Carroll County

In Carroll County outcroppings of the Wakefield Marble provide the only known backdrop for the development of caves.

Frederick County

Lying along the western border of the Lower Piedmont and Blue Ridge, Frederick County is physically composed of two regions drawing their traits from the two physiographic provinces. Eastern Frederick County, with its gently rolling lowlands, is underlain by older Cambrian/Precambrian metamorphic rock and other intrusive rocks from the Paleozoic. Sand and silt from the Tertiary have been deposited against some of the older rocks approaching the Blue Ridge; few caves are found here. Western Frederick County, west of Catoctin Mountain, is founded upon older Precambrian rocks which were thrust to the surface over the course of the Taconic orogeny. Most of Frederick County's caves can be found in this area, where local limestone formations protrude from neighboring metamorphic rock.

Garrett County

Garrett County lies almost entirely within the Allegheny Plateau physiographic region. Here the oldest rocks exposed are Devonian in age, while most others are of the Mississippian or Pennsylvanian systems. These formations settle along locally occurring faults under strain so that they appear to coincide in the linear with the older rocks of the neighboring Ridge & Valley Region. Because limestone members occur only in the upper Devonian and Carboniferous, cavern formation has been limited to areas primarily above 1,500 feet (460 m). Garrett County is home to Maryland's largest cave, Crabtree, and also contains the youngest cave-bearing rocks in state, home to Sand Cave.

Howard County

Like Baltimore and Carroll counties, formation of caves in Howard County can be found in outcroppings of Piedmont marbles—in this case, the Cockeysville formation. However, Howard County does have limestone which does contain caves, though not as extensive as in Frederick and western counties.

Washington County

Washington County contains roughly sixty percent of all known caves in Maryland. Natural forces have exposed many of the older carbonate rocks underlying the Hagerstown Valley; one such member, the Tomstown Dolomite, found at the western foot of South Mountain, is home to the largest concentration of caves in Maryland, with over 30 known caves. Other areas of notable subterranean activity occur primarily along the county’s well-established stream and creek beds, where incisions into the surrounding rock faces have allowed for increased drainage and erosion. Caves are largely concentrated around these areas of high drainage, specifically the Mount Aetna, Beaver Creek, and Antietam/Little Antietam watersheds, as well as along the massive cliffs adjacent to the Potomac River. Notable members in this region include the Stones River Limestone, Conococheague Limestone, and the Beekmantown, Elbrook, and Tonoloway formations. Washington County is also home to Maryland's only show cave, Crystal Grottoes, which will not be discussed further in this article. Note: Due to the spread of WNS throughout Maryland, all caves on C&O Canal property are closed.

Dam #4 Cave
Rattle Run entering Darby Cave
Thrust sheet of Conococheague Limestone near Fairview
Howell Cave
Entrance to Jugtown Cave
McMahon's Mill #1
McMahon's Mill #2
McMahon's Mill #3
View of Sepentroph's Hill
"The Face" is surrounded by small caves near Two Locks
Mouth of Wilson Cave


  1. Maryland Geological Survey's Caves of Maryland, 1971
  2. Virginia Region of the NSS Maryland Cave Law
  3. MGS Online
  4. Catoctin National Park
  5. The Nature Conservancy Crabtree Cave
  6. A History of Western Maryland; Scharf, 1882
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