A ribbon-cutting ceremony was held Tuesday at Great Meadows Marsh in Stratford following a $4 million restoration project.
Audubon Connecticut members, elected officials and project volunteers were among those who attended.
Officials say the salt marsh at Great Meadows spanned more than 1,400 acres, but decreased to less than half that, primarily because of development.
Officials say parts of the marsh were no longer functioning properly due to rising sea-level, among other factors.
They say the degraded marsh also produced an abundance of mosquitoes.
Thanks to $4 million in federal and state funding, 34 acres of salt marsh and other important coastal habitats have been restored.
More than 155,000 coastal plants and shrubs native to Connecticut were added to the site.
Grassy mounds were also created to provide a home for saltmarsh sparrows.
Officials say the marsh is home to many threatened plants and animals.