I know this is an old post but I have recently been looking into my great grandfather's story. He is Patrick Breen born in 1839 (best evidence so far) in County Kerry and emigrated to the U.S. in 1850. He enlisted in the U.S. Army (the "Old Army" or "Regulars" in N.Y. in 1855. He served throughout the Civil War and was discharged in 1877. At the time he was Ordnance Sergeant at Ft. St. Philip, LA.
I am interested in his Irish roots---any help?