The poster craze in the United States during the 1960s was a grassroots affair fostered by a climate of social activism. These posters made statements about social viewpoints rather than advertising commercial messages. The first wave of poster culture emerged from the late-1960s hippie subculture centered in the Haight-Ashbury section of San Francisco. Because the media and general public related these posters to antiestablishment values, rock music, and psychedelic drugs, they were called psychedelic posters. The graphics movement that expressed this cultural climate drew from a number of resources: the flowing, sinuous curves of ; intense optical color vibration associated with the brief op-art movement popularized by a Museum of Modern Art exhibition; and the recycling of images from popular culture or by manipulation that was prevalent in pop art (such as reducing continuous-tone images to high-contrast black-and-white).