What constitutes a family? Tracing the dramatic evolution of Americans’ answer to this question over the past century, provides the fullest account to date of modern adoption’s history. Beginning in the early 1900s, when children were still transferred between households by a variety of unregulated private arrangements, Ellen Herman details efforts by the U.S. Children’s Bureau and the Child Welfare League of America to establish adoption standards in law and practice. She goes on to trace Americans’ shifting ideas about matching children with physically or intellectually similar parents, revealing how research in developmental science and technology shaped adoption as it navigated the nature-nurture debate. Concluding with an insightful analysis of the revolution that ushered in special needs, transracial, and international adoptions, ultimately situates the practice as both a different way to make a family and a universal story about love, loss, identity, and belonging. In doing so, this volume provides a new vantage point from which to view twentieth-century America, revealing as much about social welfare, statecraft, and science as it does about childhood, family, and private life.