Geraghtys in County Mayo

I am searching for information regarding Geraghty's in County Mayo, Ireland. My great-great-grandfather, Patrick Geraghty, and his wife, Ann "Nancy" Kelly Geraghty, emigrated to the US in 1847. Patrick was reported to be born on 3/17/1816 and Ann on 3/17/1819. They came over with his brothers, Michael, James and John. They came in through the Port of New Orleans. Their 1st child, John, was born in New Orleans. They lived in Kentucky and Loveland, OH, before settling in Giard Township, Clayton Co, Iowa. James also settled in NE Iowa. John and Michael were believed to have settled in Chicago, IL. HIs sister, Catherine Geraghty Kielty, came to appear at some point after them and settled in NE Iowa. I am told my Aunt contacted Ireland at some point and must have known the parish they were from as she was told that the parish church had burned down and all records were destroyed.