Milligan Family

I am looking for my Milligan family from this area. My great great great grandfather, Michael Milligan, emigrated to America in the 1840s and eventually settled in Illinois. He left at least one brother behind in Ireland named John Milligan. I have a letter written from John to another brother who emigrated to Kentucky named Patrick Milligan in 1855. The letter is as follows- 

Direct in care of Edward Brown

Ballynahnich Innkeeper for me

Scribb  July 22, 1855

My dear brother Patrick,

I hope this letter will find you in as good health and spirits as I would wish.  Rose and I, thank God, are in good health.  T wrote often to you and Michael within theses last twelve months and got no answer.  I heard that my brother Michael had left Cincinnati, but I did not know where he was gone to.  You will, my dear brother, not neglect to write quickly when you get this letter and tell me now all the particulars of how you are doing and also Michael.  Let me know, too, what number of family, and the name and county of your wife.  Your aunts and uncles are in good health, but Uncle John’s wife is very ill at present.  

The state of the county is not as yet much improved.  Provision is high and money is indeed anything but plentiful.  There is indeed a very good appearance of crops, and if the potato failure keeps off this year, it will tell a good story.  The population, too, here is not more than half what it was in your time.  I hear too, that your adopted country is greatly behind what it was represented to be by newspaper accounts.  Want of employment, sickness and persecution have made it very hard for the poor, struggling Irish emigrant to settle down or live in it at all.  You know this better than I do, and I hope you will let me know in your next letter all particulars.  I hear that here a very strong combination against Irish Catholics in particular, and that the Know Nothings are a powerful and very unsparing enemy to the Irish.

Let me know how you are doing at you farm, how you are proceeding with it, what kind are your crops, and are they good this season.  I would be very glad to know about my brother Michael.  How he is, if you know, what is doing or where he is gone to.

I remain, dear Pat, your affectionate brother,

John Milligan

Any help regarding where in Ireland they are from would be greatly appreciated. One cousin believes it's Ballynahinch in Galway, but I believe it may be Ballynahinch in County Down due to this letter.