The history of the Diagnostic and Statistical Manual of Mental Disorders (DSM) reflects the larger history of American psychiatry. As the field anticipates DSM-5, it is useful to take stock of this history and consider not only how diagnosis impacts our understanding of mental illness but also how contemporary thought influences diagnosis. Before the DSM, the field was disjointed. The publication of the first American diagnostic manual, the precursor of the DSM, mirrored society's interest in organized record keeping and prevention rather than treatment of mental illness. The first and second editions of DSM brought a common language to diagnosis and were largely the work of outpatient and academic psychiatrists rather than those based in large state hospitals. The third edition of the DSM saw the shift in American psychiatry's leadership from the eminent clinician to the researcher, whereas the fourth edition reflected the rise of "evidence-based medicine." DSM-5 will likewise represent the current status of the field-not only with regard to science but also reflecting the place of American psychiatry in medicine today.