American attitudes and policies toward children with disabilities changed significantly between the 1920s and the 1950s. Drawn from a larger study of the history of child protection in the United States, I argue that a redefinition of disabled children occurred in this era. Earlier fears that feeble-minded children posed a menace to American society gave way to new anxieties that mentally retarded children placed undue strains on individual families. Both concerns encouraged the segregation and often the institutionalisation of such children, but within very different class, family, medical and policy contexts and with very different results. These developments are best understood by connecting together the emerging histories of childhood and disability through the concept of policy drift. (Contains 43 footnotes.)