The Irish contribution to Argentine history is well documented. It is estimated there are about 400,000 Argentines of Irish descent today. About 60% of those original immigrants came from the Irish counties of Westmeath, Longford and Offaly. Another 15% came from County Wexford. Argentina gained its independence from Spain in 1810 and Irish immigration increased. This included both Catholic and Protestant Irish.
Most Irish settled in Buenos Aires, however, they did not all stay there. They settled on the Pampas north and west of Buenos Aires. By the 1820 and 1830s, they settled south of Buenos Aires in the communities of Canuelas, San Vincente, Chascomus and Ranchos. By the 1840s through the 1860s the Irish moved west of the capitol to the areas of Rojas, Chacabuco, 25 de Mayo, Bragado and Saladillo.
Large collections of records for Argentina can be found on microfilm at the Family History Library. These include church registers, censuses, passports, civil registrations and passenger list. Many collections have been indexed or digitized on their website: www.familysearch.org
Eduardo A. Coughlan has written several books on the Irish in Argentina which should be consulted. Two are El Aporte de los Irlandeses a la formación de la Nación Argentina (1987) and Los Irlandeses en la Argentina (1982). Two quality websites are worth exploring. The first is the “Society for Irish Latin American Studies”: www.irlandeses.organd the Longford Westmeath Argentina Society:
www.webspawner.com/users/ldwhargentinasoc An extensive bibliography on the “Irish in Latin America” can be found on the “Irish Diaspora Studies” website: www.brad.ac.uk/acad/diaspora/guides/samerica.shtml
In case you are wondering, I have known North Americans who identified and traced their almost forgotten Argentine branch of the family and made contact with their descendants!