The island has a maximum length of about 1770 km (about 1100 mi) and a maximum width of about 435 km (about 270 mi). A great volcanic mountain chain, known as the Barisan Mountains and including several parallel ranges, traverses Sumatra, following the western coast. The highest peak on Sumatra is Kerinci (3805 m/12,484 ft). Along the eastern coast is a broad, gently sloping plain where all the main rivers flow, including the Musi, Hari, Indragiri, and Kampar, of much importance for interior navigation. The largest of the many Sumatran lakes is Lake Toba, about 80 km (about 50 mi) long. The equator passes nearly through the center of the island, and the mean annual temperature ranges from 25° to 27° C (77° to 81° F). Annual rainfall varies between 2286 and 4699 mm (90 to 185 in). Earthquakes and destructive storms, often causing injury and loss of life, are common. The soil is extremely fertile, and most of the island is densely forested; banyans, palm, rubber, and teak are among the trees found here. Fauna comprise the elephant, orangutan, siamang (black gibbon), tiger, tapir, and other animals common to the Malay Archipelago. Mineral deposits are large and include bauxite and petroleum. Agriculture, the predominant activity, is pursued on small farms or on large plantations. The principal indigenous food crops are rice, by far the largest, and corn. Estate cultivation is primarily of rubber, tea, coffee, coconuts, and spices, principally for export.

The indigenous Sumatrans belong, linguistically and culturally, to the Malayan peoples and are sometimes grouped as Indonesians. Among the most important ethnic groups are the Achenese and Gayos in the north, the Bataks in the interior, the Lampongs in the south, and the Malays throughout Sumatra. Islam is the prevailing religion. The population includes large groups of Indians, Chinese, and Arabs and some Europeans, who live principally in the coastal regions.

Marco Polo, the Venetian explorer, visited the island about 1292, and in 1509 Portuguese traders established stations here. In the 17th century the Dutch obtained a foothold on Sumatra and gradually extended their dominion. In the late 17th century the British also began establishing themselves in Sumatra. Anglo-Dutch rivalry was bitter until 1824, when the British gave up their claims to Sumatra to the Netherlands in return for Malacca. Throughout the 19th century the Dutch continued to extend their authority over local rulers; the last great struggle (1873-1903) was with the Achenese. Almost all Sumatra was occupied by Japanese troops during World War II (1939-1945), from 1942 until the conclusion of the war. Sumatra became a principal component of the Indonesian struggle for independence following World War II.' (Encarta Encyclopedia)