Human habitation of Hiiumaa can be traced back to the 5th millennium BC. Mesolithic sites in Kõpu peninsula are exemplified by the seal-hunters' settlements. There are several well-preserved grave fields of the Iron Age. In 1228, the island was first mentioned in written annals under the name Dageida. In 1254, Hiiumaa was divided between the Livonian Order and the Bishopric of Ösel-Wiek. In 1563 Hiiumaa was annexed into Sweden. In 1710, as a result of the Great Northern War the island went under the control of the Russian Empire. During World War I, the Germanmilitary forces occupied Hiiumaa in 1917. In 1918–1940 Hiiumaa was part of the Republic of Estonia, then until 1991 occupied by the Soviet Union. On demands of the Hanseatic League a lighthouse was built in Kõpu at the beginning of the 16th century. It is considered the third-oldest continuously operating lighthouse in the world, still showing its light to of the sea. Most of the farm architecture comes from the 19th century. Examples are Mihkli farming complex and Soera farm-museum with historical national artefacts.
The county is subdivided into 1 rural municipalities. The only urban settlement Kärdla is part of Hiiumaa Parish since 2017. Rural municipalities:
Hiiumaa Parish
Geography
The county includes the islands of Hiiumaa and Kassari and a number of surrounding islets. The highest point is Tornimägi hill, the longest river is Luguse, and the biggest lake is Tihu Suurjärv. In the landscapes there can be found pine forests, mixed spruce and deciduous forests, swampy thickets and juniper shrubs, coastal meadows and bogs. The most frequent tree is pine which makes about a half of forests. Pine is followed by birch, spruce and alder. In total, there are about 1,000 species of vascular plants, of which about 100 are under protection. The wildlife of Hiiumaa is remarkable. Out of 30 species of mammals, big game as elk, deer, fox, wild boar and lynx roam the island. There are about 250 species of birds on the island, 195 of them nesting. Among the Estonian counties Hiiumaa is the richest in forest – nearly 60% of the island are wooded areas. There are large marsh areas in the middle of the island. The marshes cover about 7% of its area. Cultivated land and settlements take about 23% of the area of the county.
