O’Brien (Hugh) is born in County Dublin, Ireland.

Hugh O’Brien emigrates to Boston with his parents in 1832, attends the Old Grammar School on Fort Hill, becomes a printer’s apprentice at age 12, and subsequently publisher of the Shipping and Commercial List. He subsequently lives at 2886 Washington Street. O’Brien serves on the Board of Aldermen (1876-83) and as mayor of Boston (1885-88). O’Brien dies suddenly in Somerville on August 1, 1895, and is buried in Holyhood Cemetery in Brookline.