From a recent interview:

Question: You were born in and spent the early part of your childhood in Illinois. What drew you to writing about Rodzina, who set off on an orphan train from Chicago to an unknown home?

Answer: In a bookstore in Berkeley, I found a book about the orphan trains. The cover showed a giant locomotive and a line of children, holding little suitcases. Their faces were so frightened and brave and hopeful. I knew there was a book there, and I was right.