I am an American and I normally view the "hyphens" the same way that Teddy Roosevelt did. I am one of those folks who'd do it myself or it would not get done.
It doesn't matter that the Irish were here legally or not. My point is great discrimination, hatefulness, spite, ignorance and general disdain. If someone wants the work, wants to raise their family, practices their faith, what the hell is wrong with them getting jobs here.
I used to be against illegal immigration until a certain race closed down a major highway here TWICE demanding to be GIVEN jobs and contracts.
The mexicans join hands and shut down highways getting run over trying to run, dragging their family, into this great nation in the first place.
Huh, and they still had to face the signs of "Irish need not apply".
Notice that I said "most" arrived in the first half of th 19th Century. As it turns out, however, most persons of Irish descent will discover their earliest Irish ancestors to have arrived in the 18th Century. An even bigger surprise will be that if they were churched at all they were Protestants ~ and I'm not talking about Scots-Irish, but Irish folk themselves.
The fellows coming off the prison barges (and yes, you can find out which ones on the net if you wish) had no papers, no money, little command of English, and probably knew more about fist fighting then any immigrants to America before or since.
There were even Irish people coming to America in the 17th Century, and if truth be told, probably in the 16th Century on Spanish and French ships.