From Wikipedia:

Beaver Island is the largest island in Lake Michigan and part of the Beaver Island archipelago. Once home to a unique American monarchy, the island is now a popular tourist and vacation destination.

Beaver Island is thirteen miles long, three to six miles wide, and forms part of Charlevoix County, Michigan. It is mostly flat and sandy, with large forested tracts. According to U.S. census data, the island has 55.77 square miles (144.56 km²) of land, and a year-round population of 551. The more densely settled portion, comprising perhaps one-sixth of Beaver's total land area, lies within St. James Township on the northern end. Peaine Township, taking up the remaining five-sixths of the island, contains sizable parcels of state-owned land and is mostly undeveloped.

Beaver Island lies approximately 32 miles from the city of Charlevoix on the mainland, and can only be reached by air or boat. The island has two airports, one public and one private. The ZIP code is 49782. Beaver Island is also the name of an unincorporated community comprising the settled areas of the island.