In North America, the Chesapeake Bay is the largest estuary, a semi-enclosed coastal body of water with a free connection to the open sea.

[photo, Seagull at pier, Chesapeake Beach, Maryland]

Boating Waters

Critical Area

Main Basin


Water Frontage


Seagull at pier, Chesapeake Beach, Maryland, December 2002. Photo by Diane F. Evartt.

Some 35 million years ago, a bolide (an object similar to a meteor or comet) struck the present-day Delmarva Peninsula, creating a 55-mile-wide crater. The depression created by the crater changed the course of rivers and determined the location of the Chesapeake Bay. The first indigenous people settled the Chesapeake Bay area circa 9,500 B.C. Thereafter, the Bay, as we now know it, was created about 10,000 years ago (8,000 B.C.), when melting glaciers flooded the Susquehanna River Valley. Today, fresh water from land drainage measurably dilutes seawater within the Bay.

[photo, Skipjacks under sail] The Chesapeake Bay derives its name from the Algonquian word, Chesapiooc (Chesepiuk, Chesepiook, or Chesapoic), though its exact definition is unknown. While Diego Gutiérrez first depicted the Chesapeake Bay, named Bahia de Santa Maria, on his map in 1562, a variation of its current name, Chesapiooc Sinus, was printed for the first time on a 1590 map by John White. In June 1608, Capt. John Smith led two voyages throughout the Chesapeake Bay, and identified it as the "Chesapeack Bay" on his 1612 map. In its midst, European settlers first landed at St. Clement's Island, Maryland, in 1634. Through the lower portion of the Bay, pirates settled and attacked ships off the coast. And, at its southernmost reaches during the Civil War, the first ironclads, the Confederate Virginia (formerly the USS Merrimack) and the Union's Monitor, fought to a draw near Hampton Roads, Virginia, in March 1862. Many shipwrecks, remains of vessels sunk by natural forces, human error, or attack, lie deep beneath the Chesapeake Bay.

Skipjacks under sail. Photo by Chuck Prahl.

Generations of watermen have made their living harvesting the bounty of the Chesapeake, while recreational fishing, hunting, and boating attract millions of people each year and contribute significantly to Maryland's economy. Major annual seafood harvests include millions of bushels of crabs, oysters, clams, and eels.

For ocean-going ships, the Bay is navigable with two outlets to the Atlantic Ocean: north through the Chesapeake and Delaware Canal in Cecil County, and south through the mouth of the Bay between the Virginia capes.

Further information about the Bay, including its history and effect on regional culture, may be found at the Chesapeake Bay Maritime Museum at St. Michaels.

[photo, Critical Area Commission for the Chesapeake and Atlantic Coastal Bays, 1804 West St., Annapolis, Maryland] Three Maryland agencies bear particular responsibility for Bay matters. The Department of Agriculture directs the Office of Resource Conservation which oversees Chesapeake Bay Agricultural Programs. The Department of the Environment works on behalf of the Bay through its Water and Science Administration. The Department of Natural Resources supports the work of the Critical Area Commission for the Chesapeake and Atlantic Coastal Bays (formerly Chesapeake Bay Critical Area Commission) and oversees Aquatic Resources.

Critical Area Commission for the Chesapeake & Atlantic Coastal Bays, 1804 West St., Annapolis, Maryland, December 2016. Photo by Diane F. Evartt.


Maryland 1,726 square miles
Virginia 1,511 square miles
195 miles
(widest near Cape Charles, Virginia) 30 miles
(narrowest at Annapolis) 4 miles
4,600 miles
average 25 feet
greatest (southeast of Annapolis) 174 feet
at Annapolis 1 foot
at head 2 feet
at mouth 3 feet
18 trillion gallons
(parts per thousand)
at mouth 30 ppt
midway to head 15 ppt
above fall line 00 ppt
surface to bottom 2-3 ppt


Sixteen of Maryland's 23 counties and Baltimore City border on tidal water. The Chesapeake Bay and its tributaries follow 11,684 miles of shoreline and 4,480 square miles of surface area.


rivers, creeks, streams, and smaller bays which flow into the Chesapeake Bay, the land surrounding them, and the Bay itself make up the Chesapeake Bay watershed. Three main tributaries flow into the Bay, and contribute 80% of the Bay's fresh water. The largest of these is the Susquehanna River, followed by the Potomac River, and Virginia's James River. The total number of tributaries to the Bay watershed is 419, and the watershed area itself totals some 64,000 square miles in parts of six states: Maryland, Delaware, Pennsylvania, New York, Virginia, West Virginia-and the District of Columbia. Maryland, Delaware, and Pennsylvania work together on the Bay's behalf through the interstate Chesapeake Bay Commission.
[photo, Boating at Little Round Bay, Crownsville (Anne Arundel County), Maryland] The Bay watershed provides rich habitat for an abundance of life, and some eight million of its acres are permanently preserved. In addition to resident species of fish and wildlife, the Bay supports large winter populations of migratory waterfowl and provides spawning, nursery and feeding grounds for ocean fish. This diversity enables some 2,700 different species of plants and animals to live in the Bay area.

Boating at Little Round Bay, Crownsville (Anne Arundel County), Maryland, November 2017. Photo by Diane F. Evartt.

Research on the Chesapeake Bay and its watershed is conducted by the University of Maryland Center for Environmental Science at Cambridge, and the Smithsonian Environmental Research Center at Edgewater.

According to the Chesapeake Bay Program, more than 18.3 million people live within the Bay's watershed. Scientists project that the population of the watershed will reach 21.1 million by 2040.

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