Born in New Orleans, he was the son of William Henry Hunt, Secretary of the Navy under President James Garfield. He married the grandniece of John Carroll in 1901 and converted to his wife's religion. A distinguished historian, he was variously Chief of the Division of Manuscripts at the Library of Congress, historian-general of the American Historical Association, and president of the American Catholic Historical Association. An expert in revolutionary America, one of his main interests was the relationship between Catholicism and the formation of the American nation.