Guest-edited by Richard Avedon, Harper’s Bazaar’s April 1965 issue attempted to channel the frenetic energy of a transformative moment in history. It ended up offering a glimpse of the future.

At various times, numerous people involved with the shoot—Bazaar co–art directors Ruth Ansel and Bea Feitler, fashion editor China Machado, and even Avedon—have recounted its genesis ...