Beginning in the 1890s, "defective" became a catchall term for conditions resulting from "incomplete" or "subnormal" mental and physical development. The Social Museum represented, in the terminology of the day, the blind, deaf, crippled, epileptic, feebleminded, and insane, and focused on institutions that supported the custodial care and education of these "defective classes" with the goal of helping them become self-supporting citizens. Initially, the responsibility for "defective" persons was assumed by families, local governments, or private organizations, but in the early nineteenth century a system of public charitable and correctional institutions was initiated, and asylum environments were created to shelter, educate, and possibly cure those unable to participate in an increasingly complex society. In the early 1840s, Dorothea Dix, a fierce advocate for the mentally ill, investigated living conditions in jails and almshouses across Massachusetts, conducting one of the earliest social survey projects. When the data she compiled was presented to the state legislature, funds were allocated for an expansion of the State Mental Hospital in Worcester that acted as a stimulus for the establishment of additional facilities nationwide.

Peabody described this "specialized form of charity" as a "touching service of the helpless," singling out the Massachusetts School for the Feeble-Minded, founded in 1848 by the philanthropist Samuel Gridley Howe, as "the most beautiful, as well as the most pathetic, illustration of the Christian law of service." Established to serve the needs of society's "weakest members," these asylums and schools, represented by attractive and welcoming buildings and grounds, comforting interiors, and educational and social activities, suggested to Social Museum visitors that institutions of this kind made a valuable and necessary contribution to society.