John Cosgrove was a noted lawyer, judge and Charleston civic leader. He was the son of James Cosgrove, a native of Ireland and Mary Ann Williams of Charleston. He was educated at the College of Charleston and at Georgetown University, where he received an LL.B. degree.
In 1913, he began his law practice in Charleston, becoming a partner in the firm of Logan and Grace, and later in the firm of Cosgrove and Bailey. He married Genevieve S. Connor in 1917 and they had two daughters. He was a devout churchman and enjoyed young people, especially at his summer home on Sullivan’s Island. After 1926, he was often appointed as a Special Circuit Judge and from 1930 on, he served several times as an Acting Associate Justice of the South Carolina Supreme Court. He served as President of both the Charleston and South Carolina Bar Associations. He was frequently associated with litigation out-of-state.
He disciplined himself with a keen analytical mind, read widely, and was well rounded. A forceful, logical, courteous speaker; he was very active in politics and public affairs.
He believed a lawyer owed each client his best effort and that there was never an unimportant case.
He had faith in the law and the courts.