The Blackwater National Wildlife Refuge was established in 1933 as a waterfowl sanctuary for birds migrating along the critical migration highway called the Atlantic Flyway. The refuge is located on Maryland's Eastern Shore, just south of Cambridge, Maryland in Dorchester County, and consists of over 28,000 acres (110 km2) of freshwater impoundments, brackish tidal wetlands, open fields, and mixed evergreen and deciduous forests. Blackwater NWR is one of over 540 units in the National Wildlife Refuge System, which is managed by the United States Fish and Wildlife Service.