The evolution of U.S. civil commitment law needs to be understood within the context of changes in psychiatry and medicine, as well as larger social policy and economic changes. American civil commitment law has reflected the swinging pendulum of social attitudes towards civil commitment, oscillating between more and less restriction for both procedural and substantive standards. These standards have evolved from a "need for treatment" approach to a "dangerousness" rationale, and now may be moving to a position in which these justifications are combined, particularly in the context of involuntary outpatient commitment. Civil commitment in the United States has been shaped by multiple factors, including sensitivity to civil rights, public perception of psychiatry, availability of resources, and larger economic pressures. We suggest that current American commitment practice is influenced more by economic factors and social perceptions of mental illness than by changing legal standards.