The Irish in the Civil War

The Civil War was the deadliest war in U.S. history. About 625,000 soldiers died, which computes to roughly 2% of the U.S. population in 1860.

Writing for the National Library of Ireland (NLI) blog, Gavin Finlay suggests that the American Civil War was also one of the most significant conflicts in Irish history.

Over 1.6 million Irish people lived in the United States by the 1860s and approximately 170,000 Irish-born men fought, and perhaps tens of thousands died, during the conflict (the vast majority for the Union). These figures almost mirror the numbers of Irish who fought in World War I. In other words, the American Civil War represents the second largest deployment of armed manpower in the history of Irish militarism. Indeed, recently it has been described as Ireland’s “great forgotten conflict”.

What I didn’t realize was that NLI might be a good resource for researching ancestors who served in the U.S. Civil War! In his blog, Finlay writes:

The National Library of Ireland has a number of documents, as well as dozens of books and memoirs, on Irish participation in the American Civil War that will interest any scholar or enthusiast of this fascinating period of (Irish) American history. What follows is a focus on just one set of documents the library has in its possession…

Listed as Ms. 18,327 are papers in the NLI’s manuscript collections relating to John O’Neill, originally of Portarlington, Co. Laois, who served in the Federal Army during the American Civil War, and who died in Andersonville, Georgia, in 1864. The letters and documents date between c.1860-1880s, and include some correspondence between John and his family in Portarlington. Most fascinating is a detailed and protracted correspondence between John’s mother, Dora O’Neill (and her legal representatives) and the U.S. War Department, War Pension Agency, Sanitary Commission and U.S. Treasury in Washington regarding her claim for a dependent’s war pension for her “missing presumed dead son”. Dora was ultimately successful.

Copies of some of the letters and documents have been reproduced in the blog posting, which concludes with the statement: “If you have any information about John O’Neill, we’d love to hear it…”

The writer, Gavin Finlay, completed a research internship at NLI as part of his graduate studies at Trinity College Dublin. His article can be read in its entirety at:


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