Other branches of the clan: Costello, Cassells, Costelloe, MacCostelloe, MacOisdealbhaigh, Casserly, Mac Casarlaigh, Costley, Cushely, Cuskley, Costely, Mac Giolla Choiscle.

The Costello family were an ancient race as the Annals of both England and Ireland record. We can go back to 1172, when Miles de Angulo’s son Gilbert brought his son Jocelin de Angulo with him to Ireland. It was the time of Henry II. Sir Hugh de Lacy granted him all the lands of Maghery Gallen. In the year 1195, Jocelin was granted the lands of Navan and Ardbrack and the Barons of Navan were descended from him. Costello de Angulo or Nangle obtained the title of Dynast of the Barony of Bealthaunish or Costello and the Costellos enjoyed this title until the reign of Queen Elizabeth. Milo de Angulo who married a de Burgo, a daughter of the King of Ulster. In 1193 they appear in The Annals of the Four Masters where they were called sons of Oistealb. He was a son of Gilbert de Nangle, and his family was called Mac Oisdealbhaigh. This name became MacCostello. The Costello name still occurs in the Connacht Province, in Galway, Clare and Mayo. In Mayo, it is spelt as Costello and with an "e" in Galway and Clare.

The Barony of Costello comprised the parishes of Ballaghaderreen (Castlemore and part of Kilcolman) Kilmovee ans Chariestown before 1898.

The Costello history is interesting, but I need to explain why the area is now Co. Roscommon instead of Co. Mayo as it was when the Costello family known as De Angulo, Nangle, Mac Goisdelbh, Mc Custellagh, Macguistello, Clancostillo, came to Ireland in 1172.

As far back as 1838, a Poor Law Act was introduces into Ireland as a first attempt to provide a nationwide system for the care of the poor. Parishes were so small; they had to be grouped together to form a union. Ireland had 163 unions. Each union had its own supervisory body called a Board of Guardians. Eventually they were grouped into several electoral divisions. The 1898 Local Government Act tried to bring order to the confused legislation of that time. Each area was divided into county districts, which would take over the work of the Grand Juries as regards roads and public works.

Unless each union was large enough to form a county district the boundary of the county had to be changed. Castlerea had seventeen unions in Roscommon and Ballaghaderreen and Edmondstown were in Mayo. The question was would Ballaghaderreen and Edmondstown remain in Mayo or would the boundaries be changed to allow them to remain in the Castlerea area? There was much discussion and arguments and the final decision was left to the ratepayers who decided that it would be entirely against their interest to add them to the Swinford Union. So the county borders were redrawn in favour of Roscommon. Many people did not look favourably in this and the late James Dillon of ‘Monica Duffs’ never accepted it and always had Ballaghaderreen Co. Mayo printed on his tea bags. The only question asked by strangers today is “Why do Ballaghaderreen GAA play with Mayo?” Few have the answer.

Until this time the O'Gara Clan were rulers of this area and their overlords were the O'Conors of Connaught. The O'Gara’s were routed by the newcomers the Costello's and were driven to the lands around Lough Gara, then called Lough Techet. Here they settled and Moy Gara Castle became their stronghold.

Click here for page two on the Costelloe Clan

Ballaghaderreen, Frenchpark, Fairymount and Loughglynn are part of the ancestral home of the Costelloes and form a stage of the Beara-Breifne Greenway which is based on the historic march of O'Sullivan Beara in 1603.