Whether you are looking up titans from the gilded age or from the recent past, start with World Book Web
Titans from the Gilded Age
6 Robber Barons from America’s Past
Biography: John D. Rockefeller, Sr.
The New Tycoons: John D. Rockefeller
The New Tycoons: J. Pierpont Morgan
The New Tycoons: Andrew Carnegie
James Buchanan Duke: Father of the Modern Cigarette
Titans from the recent past
The Life of Sam Walton, Founder of WalMart
The Birth of Google (Sergey Brin and Larry Page)