Until the 1970s, when they became the focus of a controversial book, the family dynamics of the Rockefeller dynasty were one of America's best-kept secrets.

That's exactly how John D. Rockefeller Sr. had always wanted it. Even in his personal letters, he avoided any intimate details or private confessions.

And yet, in all its Victorian restraint, Rockefeller's correspondence with his docile son John D. Jr. and his rebellious daughter Edith is surprisingly eloquent. Between the lines, these letters reveal the strong personalities and the sometimes strained relationships of these three very different Rockefellers.

Below is a sample of the correspondence, spanning the years 1887 to 1922:

"Dear Father" / "Dear Son"
"Dear Father" / "Dear Edith"