However, with diligent research using effective strategies the origin of an ancestor in Ireland can often be determined using North American records, opening up the Irish records of that place of origin to be explored to further document the immigrant family. Whether conducting research yourself or hiring a professional to do it, you need to remember that there are limitations to just how far an Irish family can be traced back. Success in Irish research has to be judged by different standards than, for example, Scandanavian, English or Scottish research. Most Irish Catholic and Presbyterian church records simply do not begin until the 1820s. Consequently, the average Catholic or Presbyterian lineage can only be traced back to about the year 1800.
Passenger lists for emigrants leaving Ireland are practically non-existent.
Another factor that complicates research is that Irish names can be so common that it's very hard to tell which Mary O'Connor or Patrick Kelly is the ancestor. For example, if an ancestor was a prisoner sent to Australia, penal records may provide the exact place of origin in Ireland. Often, tombstones in Canada will tell where an immigrant was born in Ireland. Not all Irish lineages will come to a halt in the early 1800s. In the case of gentry or the upper class, there are frequently extensive Irish pedigrees which can take a family back hundreds of years.