Lake Athabasca, lake in Canada, astride the Alberta–Saskatchewan border, just south of the Northwest Territories. The lake, 208 mi (335 km) long by 32 mi wide, has an area of 3,064 sq mi (7,936 sq km) and a maximum depth of 407 ft (124 m). Fed from the southwest by the Peace and Athabasca rivers (the deltas of which have separated it from Lakes Claire and Mamawi), it is drained to the northwest by the Slave River, eventually reaching the Arctic Ocean via the Great Slave Lake and the Mackenzie River. The lake was explored (1771) by Samuel Hearne, who named it Lake of the Hills. Its present name (a Cree Indian term probably for “where there are reeds”) was adopted by the North West Company when it built Ft. Chipewyan, a fur-trading post, on the southwestern shore in 1788. The only other significant settlement is Uranium City, which is important for its gold and uranium mines. The two settlements are connected (June–October) by steamer. The lake, which is economically important for commercial fishing (whitefish and lake trout), is immediately east of Wood Buffalo National Park, Canada’s largest national park.