Coordinates 54°00'N 10°00'W? / ?54°N 10°W? / 54; -10It is believed that at the end of the Neolithic Period (around 4000 BCE), Achill had a population of 500–1,000 people. The island would have been mostly forest until the Neolithic people began crop cultivation. Settlement increased during the Iron Age, and the dispersal of small forts around the coast indicate the warlike nature of the times. Granuaile maintained a castle at Kildownet in the 16th century.
Achill Island lies in the Barony of Burrishoole, in the territory of ancient Umhall (Umhall Uactarach and Umhall Ioctarach), that originally encompassed an area extending from the Galway/Mayo border to Achill Head in Co. Mayo.
The hereditary chieftains of Umhall were the O’Malleys, recorded in the area in 814 AD when they successfully repelled an onslaught by the Vikings in Clew Bay. The Anglo/Norman invasion of Connacht in 1235 AD saw the territory of Umhall taken over by the Butlers and later by the de Burgos. The Butler Lordship of Burrishoole continued into the late fourteenth century when Thomas le Botiller was recorded as being in possession of Akkyll & Owyll.
