It is about 10 acres (0.04 km2) in size and located in eastern St. James Township, Charlevoix County, Michigan.

It became part of the Michigan Islands National Wildlife Refuge in 1943.

[1] Like other islands in the Michigan Islands NWR, Hat Island was formed during the Wisconsin glaciation when a melting glacier randomly dumped a large quantity of boulders and gravel in a spot that became part of the lakebed.

The island was selected for inclusion in the Michigan Islands NMWR because of its standing as a potential breeding ground for herring gulls and other fish-eating birds.

During World War 2 it was used as a practice bombing site by the US Navy.