Fish & Wildlife Service and is composed of three islands in Lake Michigan: The three islands are largely limestone and dolomite outcroppings of the Niagara Escarpment, exhibit geology typical of changing water levels and glaciation, and rise only a few feet above the surface of Lake Michigan.

The nesting grounds of the islands support many types of colonial birds, including shorebirds, seabirds, and ducks.

Spider Island also supports a number of waterfowl species, including the American black duck, Canada geese, and the mallard.

Contrary to the original plan when the Wilderness Area was founded,[3] no public access is allowed.

Boaters are required to stay one-quarter mile (0.40 km) from shore, both to limit accidents on the rocky shoals surrounding the islands and to protect the nesting bird species.