At the end of the first millennium, the "Dál gCais" expanded into the region, against the resistance of the incumbent Uí Lochlainn and O'Conor families. The later regionally dominant O'Brien dynasty traced its origins to them. Evidence of Viking activity in the region is scant. They settled at Limerick, but in the Burren only a few artifacts of Scandinavian design have been found, centred mostly on Cahercommaun, which apparently was a major producer of wool at the time. A Viking arrowhead was found at the ringfort and a Viking hollow-bead necklace (likely dating from 820 to 850 AD) was discovered in nearby Glencurran Cave.