Be it Catholic (Green) or Protestant (Orange) Irish, a resource for finding out exactly where in Ireland ancestors once lived in Ireland is SHIP RECORDS. But Irish immigrants were coming to the US before Steam Ships, and you may find that the pre-steam ship or early steam ship era ship records are not as good as the ones you see on databases such as Ellis Island where more information was taken. On some of these ship lists there is only a surname and a headcount of family members under the surname.
I've personally run into some trouble with using ship records because of common surnames and the descendants lack of knowledge about things such as height or coloring of their ggg grandpa or ggg grandma. I also question how accurate some of those height measurements are as I found more than one ship that had hoards of men all the same height - 5 foot 6"! As for coloring, words like "fair" could mean White, Blonde, or simply lighter than other passengers on the ship from a certain country (i.e. If you're Italian you can't be "Fair!"
In one case I had over 16 possibilities. The client was upset because I was able to find one grandparent with a less common surname and a sure immigration year and village in less than an hour and the other could not be verified though I spent several hours.
So many people are "sure" they know the year of immigration but in the end they are off by a year or three. As this client was.
As a result a multitude of resources must be used.
The U.S. Census is still the backbone of American genealogy but "Ireland" is what most people reported, though sometimes - rarely - there will be a county or other commentary.
How to narrow it down? Try the World War I draft registration cards for birth dates and the name of the birth place.
Try for death records - cemetery records. The person who reported the information may not always be accurate either. I've seen "another country" as the information given, but the place the person was born should be there.
Try finding people on the census and, based on religion, search for the cemetery they were likely buried in during that era in that town, such as a church graveyard and CALL THAT CHURCH IF ITS STILL IN SERVICE to ask where they archive membership records.
Another thing that's come up is that on the ship they asked where a person was living before they got on the ship, which is not the exactly same thing as a home town village.
Many Irish immigrants went from a village to a port city and lived there a while before they got on the ship to leave the country. So it's not unusual to see "Liverpool" or "South Hampton" as the place they left or were living at before they got on the ship when the village or town they left family is different. The reason they did so was usually economic. They needed to make some money first to afford the trip. Imagine this in more modern times. These days we are supposed to change our address with the DMV within 10 days of moving but how many people manage that? So a person leaves their village, pretty sure they will never see their family again, they go to what is the Big City and work for a few months, then board the ship, make it to a town that has promises of work with other Irish immigrants, and find they have to move again and again before they "Settle."
I've heard horror stories of immigrants coming from Ireland on ships that let them starve and let them stay in filthy conditions - until the ship was close to port when people were expected to help clean the ship.
Irish came to the early Americas as servants with contracts that were almost as good as slavery. After many years - seven - twenty! They were "free" to go work somewhere else.
As a result of the conditions of immigration and living in the country, many early Irish immigrants married late or not at all and did not leave descendants.
But today, a great many Americans have that "wee bit of Irish" in them... and have made up for these deprivations for sure!
