Kim Heikkila's mother had a secret: in 1961, two years before her marriage, she became pregnant. After several months hidden in her parents' attic bedroom, she gave birth to a daughter at the Salvation Army's Booth Memorial Hospital, a home for unwed mothers in St. Paul, and surrendered her for adoption. More than 30 years later, Kim's older sister reunited with her birth family. Kim's mother had written about her experiences, but after she died,...