I’m not sure Irish immigrants were prominent in pre-Civil War south. The south had black slaves, the north had Irish slaves, lol. But the Irish slaves did get a pittance. They were my people and not always the most gracious or law abiding people.
Ante bellum New Orleans was a boom town and as such attracted a healthy share of Irish. They did much of the most difficult and dangerous work, such as digging the New Basin Canal, because slaves were too valuable. Ten thousand Irishmen died on that project.
My parish, St. Patrick’s, was founded for Irish in New Orleans in 1833, because they didn’t mix well with the native creoles. Google Margaret of New Orleans.