Volcanic island chain in the North Pacific, stretching 1,900 km/1,200 mi southwest of Alaska, of which it forms part, towards Kamchatka; population in Aleutians East Borough (2000 est) 2,700; in Aleutians West Census Area (2000 est) 5,500. There are 14 large and more than 100 small islands running along the Aleutian Trench; the largest island is Unimak (with an area of 3,500 sq km/1,360 sq mi), which contains two active volcanoes. The islands are divided into four groups: the Fox Islands, the Andreanof Islands, the Rat Islands, and the Near Islands. They are mountainous, barren, and almost treeless; they are ice-free all year but are often foggy, with only about 25 days of sunshine recorded annually. The only industries are fishing, seal hunting, and sheep and reindeer farming; the main exports are fish and furs. Unalaska is the chief island for trade as it has a good harbour. Most of the islands lie within the Aleutians National Wildlife Reserve.
The islands were settled by the Aleuts around 1000 BC and visited by a Russian expedition in 1741; led by the Danish explorer Vitus Bering. They passed to the USA with the purchase of Alaska in 1867.
As a diversionary move in conjunction with their strike against Midway during World War II, the Japanese bombed Dutch Harbor in the Aleutian Island chain and occupied Kiska and Attu islands in June 1942. In the only ground fighting on North American soil during World War II, US forces seized Attu in May 1943 and the Army Air Force soon began using it as a base for raids against the Kurile Islands. When US troops invaded Kiska on 15 August, they found the Japanese had already given up their foothold on the North American outpost two weeks earlier. The Attu battlefield is a National Historic Landmark.
The islands are of strategic importance, as Attu is the part of American territory nearest to the Asiatic mainland and the former USSR; there are naval bases and other defence installations here. Amchitka has been used for underground nuclear testing.