Edmund V. Cowdry’s Problems of Ageing (1939), the first U.S. handbook in gerontology, spurred efforts to systematize and communicate data and hypotheses in a “discouragingly difficult field,” as one of the volume’s contributors put it. Researchers, educators, and practitioners subsequently published handbooks of aging to share basic concepts, norms, and metaphors—and eventually to construct theories. Compared to theoretical constructs that animate African American studies, paradigms that inform inquiries into sex and gender, and queer theory-building, research on aging is sustained by few evidence-based, methodologically robust, heuristic theories. No single construct yet seizes the gerontological imagination. Analyzing notable handbooks reveals that the modern history of ever-emerging gerontological theory building went through three phases. First, attempts to formulate Big Theories of Aging resulted in more disappointments than scientific advances. In the second phase, researchers on aging set more modest aims, often giving priority to methodological innovation, but failed to promote consilience in a data-rich, theory-poor arena. Psychological theories, pertaining to lifespan development, merit special attention in the third phase, because they proved useful to biomedical and social scientists doing research on aging.