From secretary to Abraham Lincoln to secretary of state for Theodore Roosevelt, John Hay remained a major figure in American history for more than half a century. His private life was as glamorous and romantic as it was privileged. This first full-scale biography since 1934 is a reflection of American history from the Civil War to the emergence of the nation as a world power as Woodrow Wilson is about to take office. If Henry James or Edith Wharton...