O’Connor suffered a fatal heart attack at his Milton home on Sunday, school officials said Monday.
He spent more than 50 years as a staff member of Boston College. Before being appointed the school’s historian in 1999, O’Connor served as the chairman of the History Department from 1962 to 1970 and as a professor.
He penned numerous books and op-ed articles for the Boston Globe. A South Boston native, O’Connor explored his hometown in books including “Boston Catholics,” `’Civil War Boston” and “The Boston Irish.”
O’Connor also specialized in mid-19th century American history and the Civil War, and regularly taught graduate colloquia and research seminar courses at the college.
He served on the Bostonian Society’s board of directors, the Massachusetts Archives Commission and the President’s Commission on the Bicentennial of the United States Constitution.
O’Connor received an honorary degree from Boston College upon his retirement from full-time teaching and a local Emmy for serving as the historical consultant and narrator in a WGBH television documentary on Boston.
He received his undergraduate and master’s degrees from Boston College, before earning a doctorate from Boston University in 1957.
His colleague, Boston College history professor James O’Toole, said O’Connor was a great historian who will be missed by students and others at the college.
“It will be difficult to think of Boston College without him,” O’Toole said in a statement released by school officials.
O’Toole is survived by his wife, Mary, and children Jeanne O’Connor-Green of Milton and Michael of Newburyport. He was predeceased by another son, Steven.
O’Connor’s funeral will be held at St. Thomas More Church in Braintree on Thursday morning, school officials said.