At first, I only knew that he was from Ireland (looking for a Thomas Ryan in Ireland.... yeah, good luck with that). But awhile back, I had stumbled upon an obituary that mentioned that he was from County Cork. So now at least I could narrow him down to a county. I also had a birthdate (from his death record) and his parents' names, from his marriage record.
So when I searched birth and baptism records for Ireland on Findmypast, I hit a record for a Thomas Ryan who was born on 25 July 1831 to David Ryan and Johanna Lynch, which matched the information I had.
The record states that he was baptized in Fermoy, so now I know the specific township he was from.
Talk about the luck of the Irish!
I found a death index for a David Ryan who died in 1874 at the age of 70 in Fermoy. Although this was likely to be Thomas's father, I can't be certain without more details.
Thomas immigrated to the U.S. and settled in Boston, where he married my great-great grandmother Johanna Fitzgerald in 1860. I can't be sure when exactly he immigrated, or whether his parents or other family came with him or not.