This 350-acre reservation, administered by the Department of Conservation and Recreation, was acquired from the Massachusetts Port Authority in the late 1970s and was opened as a public park in 1985. Among the largest surviving salt marshes in Boston Harbor, Belle Isle showcases plants and wildlife now rare to the Metropolitan area. During the 1600s the marshlands were used for sheep and cattle pasture and salt marsh grasses were harvested for hay. By mid-20th century a few homes, businesses and industrial structures and a fuel tank farm were built on filled marshland as was the Belle Isle trotter track, now Suffolk Downs race track. The Suffolk Downs Drive-in Theatre was built on the site of the present Belle Isle Reservation. In 1986 a substantial wetland reconditioning program was begun.

Friends of Belle Isle Marsh, a non-profit (501c3) grassroots environmental organization, was formed in the early 1980s to help preserve the marsh and publicize its importance as an urban natural resource. We believe that protection ultimately depends on public awareness of the value and beauty of this natural resource. Our focus is mainly educational.