Lake Winnebago is a shallow freshwater lake in the north central United States, located in east central Wisconsin. At 137,700 acres (55,700 ha), it is the largest lake entirely within the state, covering an area of about 30 miles (48 km) by 10 miles (16 km) with 88 miles (142 km) of shoreline, an average depth of 15.5 feet (4.7 m), and a maximum depth of 21 feet (6.4 m). 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.