Green Bay is an arm of Lake Michigan, located along the south coast of Michigan's Upper Peninsula and the east coast of Wisconsin. It is separated from the rest of the lake by the Door Peninsula in Wisconsin, the Garden Peninsula in Michigan, and the chain of islands between them, all formed by the Niagara Escarpment. Green Bay is some 120 miles (193 km) long, with a width ranging from about 10 miles (16 km) to 20 mi (32 km).