Often we can’t find our ancestor’s origins in Ireland, no matter how hard we try. In these cases, we have to begin researching our ancestor’s sibling.
If you have an indication that an ancestor’s brother or sister joined the Mormons (LDS) in the mid-nineteenth century, then you definitely need to research that line. That branch may be your most important, especially if they immigrated to a Mormon colony in the Rocky Mountains. Since genealogy is a part of the Mormon faith, at some point, the member will have been asked where they, parents or grandparents were born. This may literally be the only place this is preserved!
Although there have been Mormon missionaries in Ireland since 1840, most Irish did not join there until the latter part of the nineteenth century. The typical convert was from a Presbyterian or Anglican background, and joined upon having already immigrated to Scotland, England or Wales. Some of the early LDS congregations in Scotland and England had large percentages of Irish born members.
This search will take you into repositories with large Mormon collections. This includes the Family History Library www.familysearch.org; the Church History Library www.lds.org/churchhistory/libraryboth in Salt Lake City.
You will find many resources available to help guide you through the vast collections of diaries, histories, genealogies and LDS Church registers. In LDS research, the problem is not that there aren’t enough records, but there too many. May we all have such problems in our research!