Cowal before it was the defended medieval homestead of the MacEwens; at first there was a palisaded enclosure, and then a promontory fort with a timber rampart. The remote areas in the north east of Cowal, which were theoretically under the dominion of Clan Lamont, were used by Scottish kings for hunting; indeed, Cowal was the last part of Britain to have wild boar. When King John Balliol was threatened by his rival, Robert de Bruys, Balliol's ally, the king of England, established Henry Percy at Carrick Castle, in the region; likewise Dunoon Castle further south. De Bruys expelled the English
Cowal subsequent invasion by Norsemen, the Hebridean islands of Dal Riata became the Kingdom of the Isles, which following Norwegian unification became part of Norway, as "Suðreyjar" (historically anglicised as "Sodor"). The remaining parts of Dal Riata attracted the name "Argyle" (later "Argyll"), in reference to their ethnicity. In an unclear manner, the kingdom of Alba was founded elsewhere by groups originating from Argyll, and expanded to include Argyll itself. However, an 11th-century Norse military campaign led to the formal transfer of Lorn, Islay, Kintyre, Knapdale, Bute, and Arran, to "Suðreyjar". This left Alba with no part of Argyll except Cowal,