Announcing the availability of the resource below, The National Library of Ireland claims that genealogy is the most popular hobby in the US, and also that there are 40M people who claim Irish descent in the US. Certainly, serving this constituency is an important activity and revenue stream for the National Library.
The best source for Irish genealogy online, offering free search over millions of names and access to Origins Exclusive records, including the definitive version of Griffith’s Primary Valuation of Ireland, the most important database for Irish genealogical research prior to the 20th century. [Irish Origins – Genealogy data for family history research in Ireland]