When Muhammad Ali knocked down Sonny Liston on May 25, 1965, a 22-year-old photographer named Neil Leifer was ringside. Decades later, the image he captured still has our attention.

On May 25, 1965, Muhammad Ali took on Sonny Liston in a rematch of their 1964 fight. The bout lasted barely more than a minute, with Ali’s “phantom punch” knocking Liston to the canvas. To ...