lake, in east-central Fort Smith region, Northwest Territories, Canada, near the Alberta border. It was named for the Slave Indians. The lake was visited in 1771 by the English explorer Samuel Hearne; (Hearne, Samuel) it was not completely surveyed, however, until the early 1920s. Fed by several rivers, of which the Slave is most important, and drained by the Mackenzie into the Arctic Ocean, the lake, with an area of 11,030 square miles (28,568 square km), is the fifth largest in North America. It is 300 miles (500 km) long and 30–140 miles (50–225 km) wide and has a shoreline indented by large bays, often with rocky slopes. Its waters are extremely clear and deep (maximum depth more than 2,000 feet 【600 metres】). The lake contains many islands and supports a fishing industry (trout and whitefish) based at the villages of Hay River and Gros Cap. The lake, linking the Mackenzie and Slave rivers, is an integral part of the Mackenzie River waterway, though ice-free for only four months.