My son-in-law's immigrant ancestor, James O'Neil came from Ireland to St Louis in the 1880's from County Armagh, Parish of Newry (which also spills over into a portion of County Down as well). The surname O'Neil[l] dots the countryside there. In his case, his Great Grandfather's family was the only Roman Catholic family--living in the all-Protestant townland of Altnaveigh within this parish.
In attempting to construct his Catholic family's genealogy, I learned--the hard way, that not only was there one Roman Catholic parish in Newry, but rather--there were officially four churches built within that faith--one was and is the celebrated St Peter's Cathedral; another was built within the township-proper, and two chapels were built just outside the township, one at Shinn (according to the Lewis' Topographical Dicionary of Ireland) and another at Glenn (according to the 1844 Irish Roman Catholic [Church] Directory! The National Library of Ireland in Dublin, had no record or listing of these other three chapels!
Just another reason why Ireland research can be so tricky!