Americans have planned for their downtowns within a continually changing framework of images and assumptions about the nature of central business districts. During each decade since World War II, discussion of downtown problems and possibilities has been dominated by a distinct set of assumptions that has conditioned academic research, federal policy, and local planning. From decade to decade, experts on downtowns have chosen different themes as central to the interpretation of downtown growth, change, and policy needs. As the understanding of the situation has changed, so have the preferred planning solutions and public interventions.