If the person you are looking for is important enough to have a book, or at least a book chapter, written about them, try searching the Contra Costa Library's catalog by typing in the name of the person. If you find a book, have it sent to your local branch and pick it up from there (unless you are lucky enough to have the book at your own branch library).
Biography.com has a good number of short biographies of important people.
Presidents of the United States - Biographies from the White House, and there are others from the White House Historical Association.
You can also look in Wikipedia for biographies, with the understanding that after reading the biography, that you check the links at the end of the biography for more information. Nothing in Wikipedia is original, and often the links lead to the source that was used to write the piece.
