This historical map of Bohuslän was published in 1729. Bohuslän had been part of the Kingdom of Svea for 71 years, yet there was certainly someone still alive who remembered the Norwegian era.
In the Icelandic and ancient sagas, Bohuslän is referred to together with Østfold as Alvhemmen. The Norwegian king Harald Hårfager conquered the area from its earl, Hrane the Goth, and made it part of the unified Norwegian kingdom, ca 870.
During the Viking Age, Bohuslän was part of the Viken, which included the coastal areas around the Oslofjord and east of the Skagerrak. The landscape was then divided into Ranrike (Old West Norse Austria) in the north and Älvsyssel (Old West Norse Elfarsýsla) in the south. The name Viken came to be used as a name for Bohuslän alone, and later specifically for northern Bohuslän, as an alternative to Ranrike.
The Dike Death around 1349 ravaged Bohuslän severely. Nearly half of the population died and 50% of the farms were destroyed. In addition, the 14th and 15th centuries were periodically very cold and population growth came to a halt. Agriculture only recovered in the 17th century.
After the dissolution of the Kalmar Union, the region became part of the Kingdom of Denmark-Norway. At the Peace of Roskilde in 1658, the entire province was ceded to Sweden, with the exception of Enningdalen.