Born in New York City in 1804, O'Conor was a second-generation Irish-American who became a successful lawyer. One of his earliest cases involved a dispute over the election of trustees for St. Paul Catholic Church, a parish in his old neighborhood.
Considered one of the greatest legal minds of his time, his name was mentioned as a possible presidential candidate. Even though he had declined the nomination, his name appeared as a candidate for the Straight-Out Democratic Party in the 1872 election. O'Conor received less than one percent of the popular vote.
Later, O'Conor was named the defense attorney for Confederate President Jefferson Davis, who was accused of treason following the Civil War.
O'Conor died on this date in 1884. his funeral was held at St. Patrick's Cathedral in New York, where he is buried in the family vault.
- Little White Book, Diocese of Saginaw