The Kings of Corco Modhruadh reigned over an area that was coextensive with the diocese of Kilfenora.
In the 12th-century, the kingdom split into Corco Modhruadh Iartharach ("Western Corcomroe") and Corco Modhruadh Oirthearach ("Eastern Corcomroe") also known as Boireann. These districts were ruled by the Ó Conchubhair Corcomroe and Ó Lochlainn families, respectively.
In the 16th-century these areas became the English administrative baronies of Corcomroe and Burren.
For further references, see Annals of Inisfallen