Hi Joe,
Thank you for your message.
Have you tried looking into their emigration? Generally more information was given at the port of arrival rather than that of departure so this may be a place to find more information and maybe even an exact place of origin. For immigration information in the US check the National Archives at http://www.archives.gov/research/immigration/
You could also try doing a search of the land records pertaining to Ireland in the 19th century. Although these do not contain any genealogical information they can sometimes be used to tie a person to a specific place. There are two:
The Tithe Applotment Books (1823-1838) found at http://titheapplotmentbooks.nationalarchives.ie/search/tab/home.jsp
and Griffith?s Valuation (1848-1864) found at http://www.askaboutireland.ie/griffith-valuation/
Have you already looked at Family Search? This is a huge database of genealogical records compiled by the Church of the Latter Day Saints. If you can find a record of some family member in this it should give you a parish name. You can search this here:
https://familysearch.org/
Some other websites which you may find helpful are:
The National Archives of Ireland http://www.nationalarchives.ie/genealogy1/genealogy-records/introduction/
The National Library of Ireland http://www.nli.ie/en/family-history-introduction.aspx
The National Archives UK ? genealogy search: http://www.nationalarchives.gov.uk/records/looking-for-person/
The Public Records Office of Northern Ireland http://www.proni.gov.uk/index/family_history.htm
I hope that this is helpful. Remember to post any new information you find. The more information you post, the more likely it is that one of our volunteers will be able to advise or assist you. Also include information concerning which sources you may have already used so others may further your search.
Kind regards,
Genealogy Support