American broadcasting, unique among media industries, relied on sponsors and their ad agencies for program content from the 1920s through the 1950s. Some sponsors broadcast educational or culturally uplifting programs to burnish their corporate images. By the mid-1960s, however, commercial broadcasting had transformed, and advertisers could only buy interstitial minutes for interrupting commercials, during which they wooed cynical consumers with entertaining soft-sell appeals. The midcentury shifts in institutional power in US broadcasting among corporate sponsors, advertising agencies, and radio/television networks reflected a fundamental shift in beliefs about how to use broadcasting as an advertising medium.