April and May — Jane Peart

It is winter 1895. Three-year-old May and her four-year-old sister, April, have reluctantly been given up by their young mother for adoption and are sent from Boston on the Orphan Train to Emeryville, Arkansas. Although their mother had requested that the sisters be placed in the same home, the girls are separated.
Upon their arrival in Emeryville, April and May are adopted by different families and go on to lead very different lives. May is taken in by Annie and Walt Chandler and is content and happy in her new home. Meanwhile, April goes to live with Ned and Peg Barstow, but tragic circumstances change April's life once again.
The two sisters grow up unaware of each other's existence, but years later, May discovers the truth about her past and begins to search for April. Will May find her long-lost sister? And if she does, will April welcome May into her life?