Julie:I have done considerable research on my father's ancestors in County Antrim and County Armagh in Northern Ireland.From the data that I have, which goes back to about 1820, I do not see a McGill/Magill link between us.
I will look closer at your OGaras.There may be a link. There were other OGara families in the Mayo area in which I am interested. I am not able to account for all of my OGaras yet.Glanmullynaha East was a small townland approx. four miles south of Charlestown. I will get back to you.