Peninsula, northeastern Wisconsin, U.S. Located between Green Bay and Lake Michigan , it was named for a strait at its tip known as La Porte des Mortes ("Death's Door").
About 80 mi (130 km) long and 25 mi (40 km) wide at its base, the peninsula was visited in the 17th century by French traders and missionaries. It is now a year-round vacation area, and tourism is a major business. The whole peninsula is popularly known as Door County, though Door is but one of four counties on the peninsula.