For centuries they were the leading sept of the northern Uí Fiachrach, a tribal group that occupied the modern counties of Mayo and Sligo. The Uí Faichrach provided successive kings of Connacht for a long period, but their sphere of influence became confined to North Connacht. In the late 10th century, their king was named Aedh Ua Dubhda (Hugh O'Dooda). He is recorded as having 'died an untroubled death' in the year 982, making this surname one of the oldest in Europe. His grandson, Mulrony, who died in 1005 had the title of Lord of Hyfiachrach. The O'Dowds were a maritime power of considerable ability in the twelfth and thirteenth centuries. On land they managed to hold their territory intact against the superior forces of the Burkes and Birminghams. Their territory at its widest embraced the túatha of Erris and Tír Amhlaidh in Mayo and Tir Fhiacrach Múaidhe in Sligo. They forged a kingdom in Uí Fiachrach Muaidhe (North Connacht) which they ringed with 20 castles, often referred to as "10-Pound Castles," and held off all comers for centuries until the incursion of the Anglo-Normans.