Most of the Irish, who settled in Pennsylvania coal regions, prior to the great Irish famine (1845-1849), came from the counties of Kilkenny and Laois, in south-central Ireland. These Irish immigrants usually had experience working in coal mines and quickly assimilated into that working environment, progressing up the ladder of promotions at a steady pace. The coal regions of Pennsylvania consisted of Lackawanna, Luzerne, Columbia, Carbon, Schuylkill and Northumberland counties. The Kilkenny and Laois Irish generally were not financially struggling before they came to America, and ended up less poor than many of the later Irish immigrants. These south-central Irish tended to commingle with Welsh and English mining families, who generally had all the supervisory positions. This commingling produced strong working and political bonds between the Welsh, English and the Kilkenny and Laois Irish.

Because of the great potato famine in Ireland in 1845-1849, a large number of Irish immigrants reluctantly descended on Pennsylvania coal regions for employment. They really never wanted to leave Ireland. These immigrants were mostly from the Irish counties of Mayo, Galway and Donegal, in north-west Ireland, where the famine hit the hardest. These Irish immigrants did not have skilled mining backgrounds and were mostly farmers and basic laborers, trying to escape starvation in Ireland. Coming to Pennsylvania was more a necessity than a privilege to them. They were financially destitute and did not even have much wealth to get started on. These two factors lead to these Irish immigrants ending up in the rough and poor areas of Pennsylvania. Needless to say, the north-west Irish, in the coal regions, did not get along with the south-central Irish of Kilkenny and Laois, who had already bonded with the Welsh and English years before.

Welsh and English minors had come from a background in England of organized labor practices. In Pennsylvania, attempts were made in the 1860’s to organize coal mine labor into unions. First attempts consisted of including all miners in unions, regardless of ethnicity. Since the Welsh and English were being treated better than the Irish, by management, these early attempts failed as arguing and fighting broke out between the Irish and other groups culminating in the "Molly McGuire" violent era around 1863-1867. During this period, the Kilkenny and Laois Irish generally sided with the English and Welsh immigrants. As well, the Molly McGuire Irish were Catholics, whereas many of the earlier Irish immigrants were Protestant. After a few years, some arrests and executions, this labor movement ended with tolerable agreements between the parties.

Anthracite Mining in Pennsylvania declined in the 1950’s, but the Irish culture is still very influential in the mining counties heavily populated by Irish descendants. Many old traditions still exist, as well as influential Irish groups and festivals; although this has slowly faded as Irish descendants mix with descendants of other cultures.