Under the name Båhuslen (Bohuslen in Danish), it was a Norwegian county from the Norwegian conquest of the region from the Geats and subsequent unification of the country in the 870s until the Treaty of Roskilde in 1658, when the union of Denmark–Norway was forced to cede this county, as well as Skåneland (part of Denmark proper), to Sweden.

The geography is distinguished by the rocky coast, bordering an archipelago: there are about 3,000 islands and 5,000 islets (skerries).

In old days, the seascape was renowned for its many reefs and sunken rocks which caused many shipwrecks.

[citation needed] Bohuslän's coastline was ranked 7th among the world's last great wilderness areas by CNN Travel.

[3] In detail these granites have been eroded as to contain abundant small rock basins, some of them filled with clay and silt of combined glacial and marine origin.

When Norway was united with Denmark, the province began its decline in wealth; the area was frequently attacked by Swedish forces as part of the larger border skirmishes.

Being a border zone towards the Swedish kingdom, and to a lesser extent against Danish lands in Halland, the Båhus region was disproportionately populated by soldier families.

Before the large scale fishing of herring started, Bohuslän had a considerable forest cover.

But with the increased importance of fishing, more wood was needed as construction material for houses and boats, and as fuel for herring oil boilers (trankokerier).

The Nordic Bronze Age (c. 1700–500 BCE) produced rock art showing scenes from the daily life and religious rituals, such as the examples found in Bohuslän.

The rock art at Tanum, possibly made earlier, c. 2,500 to 3,000 years ago, have been entered as a site in the UNESCO World heritage program.

The carvings portray the life of an agricultural society with images of daily life, with human figures, religious rituals, ships, circular objects, soles, animals, and fertility figures (e.g. phalluses); and the creation of shallow bowls.