Sandy Island Beach State Park is part of the Eastern Lake Ontario Dune and Wetland System, a 17 mile stretch which extends from the Town of Richland, Oswego County, north along Lake Ontario to Jefferson County. The Dunes were formed by wind and wave motion of a giant inland sea that preceded Lake Ontario. The area is the only significant freshwater dune site in the northeastern United States. The Eastern Lake Ontario Dune system offers many opportunities for hikers, birdwatchers, canoeists and kayakers. Walkovers and viewing platforms have been built to protect the fragile dune environment.