Dickinson Island/Harsen's Island Marshes

Algonac Prairie and Oak Savanna location


  • Nominated for Legal Dedication
  • The Nature Conservancy Natural Areas Registry

Size: 2,110 acres

Location: At the mouth of the St. Clair River, 25 miles northeast of downtown Detroit

Management: St. Clair Flats Wildlife Area

Activities: Birdwatching, canoeing, hunting, non-motorized fishing, photography, scenic vistas

Importance: Besides being the largest freshwater delta in the Great Lakes Basin (and one of the largest in the world), the St. Clair River Delta contains the greatest area of unaltered coastal marsh in southern Michigan and perhaps the State. It is a well-known stop-over for migrating waterfowl, and provides nesting habitat for other birds, including the state-threatened common tern. Only four other delta wetlands are known in Michigan.

On Dickinson Island, small areas of wet prairie exist between the oaks on the ancient delta formation and sedge meadow of the younger delta wetland. Wet prairie sites on both Dickinson and Harsen's Islands provide habitat for rare plant species. Other animals species include great blue heron (which nests on the islands), the eastern fox snake (state-threatened and restricted to coastal marshes of Saginaw Bay, Lake St. Clair, and Lake Erie), king rail (declining and listed as endangered in Michigan), and the rare Forster's tern (nests on the channel levees that extend west from Dickinson Island).


Dickinson Island marshes

Great Lakes marsh

Photo by Denny Albert

Dickinson Island