O'Brien, O'Neill, Limerick

Hi,

 I am looking for additional information on my husband's gggrandmother Mary Ann O'Neill (1845-1921).  She must of traveled to Wales and married Daniel G. O'Brien and had many children. I believe Daniel was a coalminer in Wales.  She eventually moved to the Tamaqua area in the coal region of Pennsylvania.  She married Benjamin Williams after Daniel died.   Her parents were Jeremiah O'Neill and Charlotte Limerick.   Her tombstone states that she was the wife of Benjamin Williams, born in Union Hall, Cork, Ireland.  

From the web it seems like Union Hall is a fishing village.  Did many people leave to find work in Wales and eventually to the coal regions of the USA?  Any information would be great.   Jackie