Aleutian Islands (əlōˈshən) [key], chain of rugged, volcanic islands curving c.1,200 mi (1,900 km) west from the tip of the Alaska Peninsula and approaching Russia's Komandorski Islands. A partially submerged continuation of the Aleutian Range, they separate the Bering Sea from the Pacific Ocean. The Aleutians comprise four main groups: Fox Islands, nearest to the mainland, including Unimak, Unalaska, Umnak, and Akutan; Andreanof Islands, including Amlia, Atka, Adak, Kanaga, and Tanaga; Rat Islands, including Amchitka and Kiska; and Near Islands, the smallest and westernmost group, including Agattu and Attu. The Semichi Islands, of which Shemya is the largest, are nearby.
The Aleutians have few good harbors, and numerous reefs make navigation treacherous. Among active volcanoes is Mt. Shishaldin, on Unimak. Relatively moderate temperatures lead to heavy rains and constant fog. Almost treeless, the islands have a luxuriant growth of grasses, bushes, and sedges. Most of the islands are within the Aleutian National Wildlife Reserve. Sheep and reindeer are raised. Hunting and fishing are the main occupations of the Aleut population. Research stations and military bases are located on the islands; Amchitka has been used for underground nuclear tests.
The Aleutians were visited in 1741 by Vitus Bering, a Danish explorer employed by Russia. The indigenous Aleuts were exploited by the Russian trappers and traders who, in search of sea otter, seal, and fox fur, established settlements on the islands in the late 18th and early 19th cent. The islands were included in the Alaska purchase in 1867; after the purchase, the U.S. government forbade seal trapping except by Aleuts. Fishing and fur hunting are now controlled by the federal government. Dutch Harbor, on Unalaska, became a transshipping point for the gold boomtown of Nome in 1900. The Aleutians were important during World War II; in 1940, a U.S. naval base was established at Dutch Harbor. In 1942 the Japanese bombed the base and later occupied Attu, Kiska, and Agattu islands; a U.S. counterattack from bases on Adak and Amchitka regained them in 1943.