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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. It was created more than 10,000 years ago when glaciers melted and flooded the Susquehanna River Valley. Today, fresh water from land drainage measurably dilutes seawater within the Bay.
[photo, Seagull at pier, Chesapeake Beach, Maryland]
  • Charting the Chesapeake, 1590-1990
  • Boating Waters

    Critical Area

    Main Basin


    Water Frontage


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

    [photo, Skipjacks under sail]

    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.

    Native Americans living along its shores gave the Bay an Algonquin name. Chesepiook, meaning "great shellfish bay," was used to signify the abundance of Bay crabs, oysters, and clams. The Bay was the site of the first English settlement in Maryland and later saw the Civil War confrontation between the iron-clad Confederate Merrimac and the Union's Monitor in 1862. Generations of watermen have made their living harvesting the bounty of the Bay, 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.

    Skipjacks under sail. Photo by Chuck Prahl.

    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 Science Services 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.

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



    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 rivers, creeks, and streams which flow into the Bay, the land surrounding them, and the Bay itself make up the Chesapeake Bay watershed. Main tributaries - Susquehanna River, Potomac River, James River - contribute 80% of the Bay's fresh water. Total tributaries: 419. Watershed area: 64,000 square miles in parts of six states-Maryland, Delaware, Pennsylvania, New York, Virginia, West Virginia-and the District of Columbia.

    The Bay watershed provides rich habitat for an abundance of life. 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 results in 2,700 different species of plants and animals living in the Bay area. The University of Maryland Center for Environmental Science conducts research on the Chesapeake Bay and its watershed.

    Watershed population was 16.6 million in 2006, up 5.2 percent from 2000. Scientists project that the population of the watershed will exceed 18 million by 2020.

    Chesapeake Bay Commission
    Chesapeake Bay Critical Area Commission
    Chesapeake Bay Trust
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     Maryland Manual On-Line, 2009

    July 1, 2009   
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