At the end of "Desiree's Baby," Armand discovers a letter from his mother to his father. She writes,
"But above all . . . night and day, I thank the good God for having so arranged our lives that our dear Armand will never know that his mother, who adores him, belongs to the race that is cursed with the brand of slavery."
From the letter, Armand realizes that his mother is part black and that he has expelled his wife and child from his home for something that is connected to him, not to Desiree. Armand's reason for forcing Desiree to leave would have been socially acceptable during the pre-Civil War time period--a truth that his mother had realized and taken precautions against. This is why she chose to live in France, a more forward-thinking country at that time, where she and Armand's father could maintain their relationship in peace; for in the United States, mixed-race marriages were not simply socially unacceptable, they were dangerous and illegal for their participants.