Shetland Islands,island group and council area,551 sq mi(1,427 sq km), extreme N Scotland, NE of the Orkney Islands. Formerly the county of Shetland. or Zetland [zet'–] , the archipelago is 70 mi (110 km) long and consists of some 100 islands, of which fewer than one fourth are inhabited. Mainland, Yell, Unst, Fetlar, Whalsey, and Bressay are the largest islands. Lerwick, on Mainland, is the principal town of the Shetland Islands. The surface of the islands is generally low and rocky, with few trees and spare soil. In places cliffs rise above 1,000 ft (305 m). The climate is humid and, despite the northern latitude, rather mild. Oats and barley are the chief crops; fishing and cattle and sheep raising are very important. The region is famous for its knitted woolen goods and for the small, sturdy Shetland ponies originally bred there. With the discovery of North Sea oil in the early 1970s, a major oil terminal was built at Sullom Voe in the north of Mainland. Tourism is also significant. The Shetlands are known for their ancient relics. Pictish forts are scattered throughout the islands, and a village from the Bronze Age has been unearthed at Jarlshof on Mainland. By the late 9th cent. the islands were occupied by the Norsemen; traces of their speech and customs survive. The Shetlands were not annexed to Scotland until 1472, when the islands were taken over as an unredeemed pledge of King Christian I of Norway and Denmark for the dowry of his daughter, Margaret, who married James III of Scotland.