In the ninth and tenth centuries it covered the Northern Isles (Norðreyjar) of Orkney and Shetland, as well as Caithness and Sutherland on the mainland.

[4] However, Sigurd's line barely survived him and it was Torf-Einarr (ruled c.895–910), Rognvald's son by a slave, who founded a dynasty that controlled the islands for centuries after his death.

[5][Notes 1] He was succeeded by his son Thorfinn Skull-splitter (c.910–963) and during this time the deposed Norwegian King Eric Bloodaxe often used Orkney as a raiding base before being killed in 954.

Thorfinn's death and presumed burial at the broch of Hoxa, on South Ronaldsay, led to a long period of dynastic strife.

[Notes 2] Thorfinn the Mighty (c.1025–1064) was a son of Sigurd and a grandson of King Malcolm II of Scotland (Máel Coluim mac Cináeda).

[17] In 1290, the death of the child princess Margaret, Maid of Norway in Orkney, en route to mainland Scotland, caused a disputed succession that led to the Wars of Scottish Independence.

[19] In 1468 Orkney and Shetland were pledged by Christian I, in his capacity as King of Norway, as security against the payment of the dowry of his daughter Margaret, who was betrothed to James III of Scotland.