Dexter Marsh is a 1,350-acre wetland at the eastern end of Lake Ontario in Dexter, New York. Managed by the New York State Department of Environmental Conservation as the Dexter Marsh Wildlife Management Area, it is both a protected wetland and a National Natural Landmark, a status it received in May 1973. It is significant as a relatively undeveloped bay-head area on the Great Lakes. Unlike many Lake Ontario wetlands, it has no barrier beaches and is directly exposed to the lake’s winds and waves. It is also known as a migratory bird layover and a popular place for fishing and trapping.