This new interpretation of the structure and meaning of the Happenings produced by Allan Kaprow (1927–2006) and Claes Oldenburg (b. 1929) in the late 1950s and 1960s sheds light on the context, theoretical framework, and working practice unique to this groundbreaking artistic form. Drawing on extensive archival research and including never-before-published drawings by Oldenburg, Robert E. Haywood describes the dialogue – at times contentious – between these two artists about the direction of the Happenings and modern art in general. Through a comprehensive analysis of these often overlooked works, it becomes clear that the Happenings—born in the midst of Cold War tensions and an increased uneasiness with the direction society was taking—challenged the traditional definitions of art in innovative new ways and were a critical component in the development of the art of the 20th century.