Perhaps best known for providing age-related norms in early development, norms that are still used as a basis for measures of developmental maturity, Arnold Gesell was a key figure in developmental psychology from the 1920s through the 1950s. After examining Gesell's reputation and status in the field, we explore Gesell's changing relationship to eugenics, both in terms of Gesell's often contradictory attitudes about the role of hereditary and environmental influences in development, and in terms of the broader relationship between the eugenics movement and science.