This impeccably researched and stylishly written family history traces the O Callaghans (Callaghan, Callahan) from their mythic beginnings in Ireland to their present-day progeny in County Cork, Spain, the United States, Australia, and other places. Prepared by Joseph F. O Callaghan, distinguished professor emeritus of medieval history at Fordham University, Clan Callaghan is the standard against which all future studies of this family will be measured. Adding to the volume's historical value, Professor O Callaghan has provided sixteen genealogical charts that outline numerous O Callaghan lines.