Lake Winnebago is a shallow freshwater lake in the north central United States, located in east central Wisconsin. At 137,700 acres it is the largest lake entirely within the state, covering an area of about 30 miles by 10 miles, with 88 miles of shoreline, an average depth of 15.5 feet, and a maximum depth of 21 feet. It has many shallow reefs along the west shore, and a drop-off type shoreline on the east. There are several islands along the west shore.