Maryland’s geography packs five landform regions into 32,133 km² (12,407 sq mi), the ninth-smallest state. From east to west they are the flat Atlantic Coastal Plain, split by the Chesapeake Bay into the Eastern and Western Shores; the rolling Piedmont of central Maryland; the narrow Blue Ridge, made up of Catoctin Mountain and South Mountain; the Ridge-and-Valley belt of Washington and Allegany counties; and the Appalachian Plateau in the far west. The highest point is Hoye-Crest on Backbone Mountain in Garrett County, about 1,024 m (3,360 ft), near the West Virginia line. The lowest is sea level along the Atlantic shore at Ocean City and Assateague Island. The state’s main river is the Potomac, which forms most of its southern border with Virginia and West Virginia, and its defining water body is the Chesapeake Bay, the largest estuary in the United States, which nearly cuts the state in two.
That range of landscape in so small a space is why Maryland is nicknamed “America in Miniature”. This guide crosses the regions in order, from the ocean to the West Virginia border.
The Eastern Shore: Assateague’s Dunes and the Blackwater Marshes
The counties east of the Chesapeake Bay form the Eastern Shore, Maryland’s part of the Delmarva Peninsula, which it shares with Delaware and two Virginia counties. This is the lowest, flattest land in the state, built of sand, silt and clay laid down by rivers and shallow seas, and much of it stands only a few metres above the tide.
On the ocean side, Assateague Island is a barrier island 60 km (37 mi) long, with its northern two-thirds in Maryland and its southern third in Virginia. It is protected as Assateague Island National Seashore, with Assateague State Park on the Maryland end, and it is known for its feral horses. The island is a reminder that barrier coasts move: it was once joined to Fenwick Island, where Ocean City now stands, until the Chesapeake–Potomac hurricane of 1933 cut an inlet between them. Jetties built between 1933 and 1935 kept that inlet open for navigation, and Assateague has since migrated westward, away from the Ocean City shore.
The bay side of the Eastern Shore is a maze of tidal marsh. Blackwater National Wildlife Refuge, set up in 1933 about 19 km (12 mi) south of Cambridge in Dorchester County, protects more than 110 km² (28,000 acres) of brackish wetland, freshwater impoundments and forest on the Atlantic Flyway. Its name comes from the tea-coloured water of the Blackwater River, darkened by tannins leached from peat.
Chesapeake Bay and the Western Shore’s Calvert Cliffs
The Chesapeake Bay runs about 320 km (200 mi) from the mouth of the Susquehanna River at Havre de Grace to the Atlantic between Cape Henry and Cape Charles in Virginia. It is only 4.5 km (2.8 mi) wide at its narrowest point in Maryland, between Kent County and Harford County, and about 48 km (30 mi) wide at its broadest, just south of the Potomac’s mouth. For such a large body of water it is remarkably shallow: the average depth is 6.4 m (21 ft) and the deepest point about 53 m (174 ft). Counting every tidal creek and river, its shoreline stretches 18,804 km (11,684 mi), and its drainage basin covers 166,534 km² across six states and Washington, D.C. Sixteen of Maryland’s 23 counties, plus Baltimore City, touch its tidal waters.
Almost all of Maryland drains to the bay. The exceptions are small: a corner of far western Garrett County drained by the Youghiogheny River to the Mississippi, the eastern half of Worcester County draining to the Atlantic coastal bays, and a sliver of the northeast that drains toward the Delaware River. Until 1952, crossing the bay meant taking a ferry; that year the Chesapeake Bay Bridge opened between Sandy Point, near Annapolis, and Kent Island.
The Western Shore of the Coastal Plain, south of Annapolis, is slightly higher and more dissected than the Eastern Shore. Its most striking feature is the line of cliffs along the bay side of the Calvert Peninsula, which runs for about 40 km (25 mi) from Chesapeake Beach to Drum Point and stands 20 to 40 m (66 to 131 ft) high. The cliffs expose the Calvert Formation, sediment laid down on a shallow sea floor roughly 18 to 15 million years ago in the Miocene, along with the younger Choptank and St. Marys formations. They yield fossil shark teeth, including those of megalodon, and collecting is allowed on the beach at Calvert Cliffs State Park, though the eroding cliffs themselves are closed.
The Fall Line and the Piedmont: Great Falls to Sugarloaf Mountain
Where the soft Coastal Plain sediments meet the hard, ancient rock of the Piedmont, rivers drop over rapids and waterfalls. This boundary is the fall line, and it explains where Maryland’s biggest city grew up. Baltimore sits right on it, near where the Patapsco River empties into the bay, and the line divides the city into a “lower city” on the Coastal Plain and an “upper city” on the Piedmont; streams such as Jones Falls cut down through it to the Inner Harbor. Mills could harness the falling water, and ships could sail up to the foot of the rapids but no further. Much of the Baltimore–Washington corridor straddles this line.
The fall line’s showpiece is the Great Falls of the Potomac, 23 km (14 mi) upstream of Washington, D.C. Because the Maryland–Virginia boundary follows the low-water mark on the Virginia bank, the river and the falls themselves belong to Montgomery County, Maryland. The Potomac drops a total of 23 m (76 ft) in less than 1.6 km (1 mi), over a series of 6 m (20 ft) falls, before squeezing through Mather Gorge. The rocks are schists and gneisses about 750 million years old, but the falls are young: they formed during the last glacial period, about 35,000 years ago, when a fall in sea level made the river cut down into its valley.
Inland, the Piedmont is a landscape of rolling hills, dairy farms and deeply cut stream valleys stretching through Montgomery, Howard, Carroll, Baltimore and Harford counties. Maryland has no natural lakes, because no ice sheet ever reached it to scoop out basins, so every lake here is a reservoir. On the lower Susquehanna, Conowingo Dam is the largest dam in the state.
Near the Piedmont’s western edge stands Sugarloaf Mountain, an isolated hill about 16 km (10 mi) south of Frederick. Its summit is 391 m (1,283 ft) above sea level and about 244 m (800 ft) above the surrounding farmland, which makes it visible from much of northern Montgomery County. It was named a National Natural Landmark in 1969.
Catoctin Mountain and South Mountain: Maryland’s Blue Ridge
West of Frederick the ground rises abruptly into the Blue Ridge, which in Maryland is only two ridges wide. Catoctin Mountain is the easternmost ridge of the whole Blue Ridge chain. It runs about 80 km (50 mi) from near Emmitsburg south past the Potomac at Point of Rocks into Virginia, and it reaches its highest point, about 580 m (1,900 ft), just southwest of Cunningham Falls State Park.
South Mountain, the next ridge west, is the northern extension of the Blue Ridge into Maryland and Pennsylvania. It begins at the Potomac near Knoxville as a narrow ridge only about 370 m (1,200 ft) high and grows taller and wider northward. Its summits include Lambs Knoll at 536 m (1,758 ft) and, near the Pennsylvania line, Quirauk Mountain, which at about 660 m (2,150 ft) is the range’s highest point in Maryland. The Appalachian Trail follows the crest of South Mountain across the state.
Hagerstown Valley and Sideling Hill: the Ridge-and-Valley Belt
Beyond South Mountain the land drops into the Hagerstown Valley, Maryland’s section of the Great Appalachian Valley, which continues north as the Cumberland Valley in Pennsylvania and south as the Shenandoah Valley in West Virginia and Virginia. The valley floor is limestone farmland drained by Antietam Creek and Conococheague Creek, both flowing south to the Potomac.
West of the valley begins the Ridge-and-Valley province, long parallel ridges of folded sandstone separated by narrow valleys of softer shale and limestone. This is where the state is pinched to less than 3.2 km (2 mi) wide at Hancock, and where the geology is laid open most dramatically. Sideling Hill, about 8 km (5 mi) west of Hancock, is a syncline: a ridge formed where rock layers are folded downward, capped by hard Mississippian Purslane Sandstone. When Interstate 68 was built across it, engineers blasted a notch 100 m (340 ft) deep through the ridge, finishing in August 1984. The cut exposes about 250 m (810 ft) of tightly folded strata and is regarded as one of the best rock exposures in the northeastern United States.
The Potomac River, 652 km (405 mi) long, crosses this belt by cutting water gaps through ridges such as Sideling Hill rather than going around them.
Backbone Mountain and Deep Creek Lake: the Appalachian Plateau
The westernmost region begins at the Allegheny Front, the escarpment that separates the Ridge-and-Valley from the Appalachian Plateau (called the Allegheny Plateau locally). In Maryland the front rises more gently than it does farther north in Pennsylvania, and the name is seldom used, but Dans Mountain near Cumberland marks it, with Dan’s Rock reaching about 882 m (2,895 ft). West of it lies Garrett County, a high, rolling upland of forest and farmland that is part of the wider Appalachian Mountains.
Backbone Mountain is a ridge about 63 km (39 mi) long running from Tucker County, West Virginia, to the Savage River Reservoir. Hoye-Crest, just inside Maryland, is the state’s summit. The Eastern Continental Divide follows part of this ridge: rain falling on one side reaches the North Branch of the Potomac and the Chesapeake Bay, while rain on the other side feeds the Youghiogheny River, the Ohio and eventually the Gulf of Mexico.
On the Youghiogheny side lie the plateau’s best-known waters. Deep Creek Lake is a reservoir created when Deep Creek Dam was finished in 1925 for a hydroelectric plant; it covers about 16 km² (3,900 acres) with 111 km (69 mi) of shoreline, and the state bought it in 2000. Northwest of Oakland, Swallow Falls State Park holds Muddy Creek Falls, at 16 m (53 ft) the highest free-falling waterfall in Maryland, along with a stand of hemlocks more than 300 years old.
The climate follows this climb, from humid subtropical on the Coastal Plain to humid continental from the Cumberland Valley westward. For a closer look at the water body that ties all five regions together, see our guide to the Chesapeake Bay.