Actually poppagator, the vast majority of Irish immigrants to the US prior to the Famine was largely rural, and made up of Ulster Protestants, not Irish Catholics. It was these Ulster Protestants who migrated almost exclusively to the rural south, where they became the "cracker" culture, and gave birth to the Ku Klux Klan.

Irish Catholic immigration was almost exclusively urban during and after the Famine, and was initially limited to the northeastern US (ie Boston, NY, Philadelphia, etc). It was later that these immigrants moved west, building the transcontinental railroad, moving to the stockyards of Chicago, that sort of thing.