Gene Stratton-Porter (birth name Geneva Grace Stratton) was a 19th-century author nature books and children's books noted for their heavy use of natural themes and promotion of conservation. Her best known works are Freckles and A Girl of the Limberlost.The Other Wiki has more here.
Ambiguous Gender: The Scout Master in The Keeper of the Bees also has a Gender-Blender Name and the narration is very careful not to use pronouns, save in one place where "he" is unavoidable. The Scout Master has taken extreme pains to keep her gender a secret.
Blue Blood: Even American characters often have long pedigrees.
Bride and Switch: In The Keeper of the Bees, a young woman tells Jamie there is an unborn baby who needs a father. Jamie assumes she's speaking of herself and, having fallen in love with her on sight, agrees to marry her. When they call him to collect the baby, the mother is not the girl he married; it's her sister.
In the Blood: On her 18th birthday, in Her Father's Daughter, Linda receives a letter from her deceased father. Before she opens it, she tells the man with her that she is quite certain that it tells her that Eileen is not really her father's daughter and not really her sister.
Before I open this envelope I am going to tell you what I believe it contains. I have not the slightest evidence except personal conviction, but I believe that the paper inside this envelope is written by my father's hand and I believe it tells me that he was not Eileen's father and that I am not her sister. If it does not say this, then there is nothing in race and blood and inherited tendencies."
I Will Wait for You: In Her Father's Daughter, Donald's mother is very firm with him about how he should not ask for this.