It runs east-west along the southern coasts of Mississippi and Alabama, from the mouth of the Pearl River at the Mississippi-Louisiana state border to the Dauphin Island Bridge, a distance of about 90 miles (145 km).

The expansion of the St. Bernard subdelta slowly isolated the Mississippi Sound from ocean dynamics of the open Gulf of Mexico.

[1] Traditional seafood harvests, particularly shellfish, have been curtailed recently due to declines in numbers and quality caused by pollution and weather related events such as hurricanes, flooding, or droughts.

Federal and state authorities have various programs and regulations aimed at shellfish restoration and water quality monitoring for beachgoers.

[2][3] After the 2008 and 2011 openings of the floodgates of the Bonnet Carré Spillway the massive freshwater destroyed the oyster and crab populations and the authorities have undertaken cultch plantings to restore the fisheries in the western sound.