On January 26, 1957, Richard Hamilton wrote a now-famous letter outlining his definition of what 'Pop Art Is'. This volume celebrates the fiftieth anniversary of Hamilton's prophetic document, presenting the works of more than forty artists from his own generation of Pop artists (among them Hamilton himself, Robert Rauschenberg, Jasper Johns, and Andy Warhol) and from artists of subsequent generations who have contributed to the development and dissemination of Pop Art (Jeff Koons, Richard Prince, Mike Kelley, Damien Hirst, and others).A text by Greil Marcus, a photographic essay by Louise Lawler, and an interview with Robert Venturi and Denise Scott Brown by Dan Graham are included in the book, which illuminates the powerful, international impact of Pop Art throughout the second half of the 20th century. Pop represented a sudden and dramatic expansion of often-contradictory possibilities, and for this reason and others the concept of Pop remains vital in contemporary art.