The O'Leary family history traces its roots primarily to Ireland, where the surname is derived from the Gaelic name Ó Laoghaire, meaning "descendant of Laoghaire." The name is associated with several regions in Ireland, particularly County Kerry and County Cork. Many O'Learys emigrated during the 19th century, particularly during the Great Famine, seeking better opportunities abroad. In the United States, the O'Leary family has made notable contributions in various fields, including politics, sports, and the arts. One famous figure is Mrs. O'Leary's cow, which is often humorously blamed for starting the Great Chicago Fire of 1871, although this story is largely considered a myth.