For a long time timber had been transported along the river and both sawn and un-sawn wood were important commodities. Many ships came sailing to buy wood. Once Bohuslän became Swedish through the Roskilde peace agreement in 1658, the government in Stockholm soon became interested in establishing a trading area in the north of Bohuslän, as well as making the new province more Swedish. The Swedish government had previously legalised against all trade from loading areas and maintained that trade should only be carried out from towns. Therefore the north of Bohuslän must get its own town. The new town should also be fortified and able to defend the newly acquired county. When a site for the new market town was to be chosen, Strömmen was selected, probably because of the good harbour and the possibilities of building forts in the hills to defend the town. Strömmen received its first municipal charter in 1667 and a town charter soon after.