King Charles IX of Sweden founded the town of Mustasaari/Mussor on October 2, 1606, around the oldest harbour and trade point around the Korsholm church approximately seven kilometres (4.3 miles) to the southeast from the present city.
Kong Karl 9. af Sverige grundlagde byen Mustasaari (eller Mussor) den 2. oktober 1606 ved ved den gamle havn og marked tæt ved Korholm-kirken, ca 7 kilometer sydøst for den nuværende by.