When the Avalon Ballroom and Bill Graham's Fillmore Auditorium began to hold weekly dance concerts, Wilson was called upon to design the posters. He created psychedelic posters from February 1966 to May 1967, when disputes over money severed his connection with Graham. Wilson pioneered the psychedelic rock poster. Intended for a particular audience, "one that was tuned in to the psychedelic experience," his art, and especially the exaggerated freehand lettering, emerged from Wilson's own involvement with that experience and the psychedelic art of light shows.