The year 2010 marked the 100th anniversary of Karl William Kapp’s birth and provides this publication of his Foundations of Institutional Economics with a special occasion. Yet, as will be explained below, this book does not merely serve a commemorative purpose. This Introduction leaves to future research the task of a more comprehensive evaluation of Kapp’s contribution to economics, and of his potential signifi cance to modern pluralist and heterodox economics. It focuses instead on understanding Kapp’s book within the context of his intellectual project and his personal biography. In this, the Introduction answers questions that have arisen from the manuscript’s history: for instance, why was the author unable to complete this work for 16 years? And why should this material be published at this point in time after being stored largely unnoticed in the Kapp Archive for well over 30 years? 1 Thus, the Introduction is a continuation of the “rational reconstruction” of (European) institutionalism 2 and supports the theory that Kapp’s book was part of a largely unexplored project in twentieth-century institutionalism. The goals of this project were to “institutionalize” institutional economics internationally via organizations of importance; to move the development discourse in the direction of democratic planning of social welfare minima, technology and the environment; and to prevent the global rise of “formal” economics. While more research is certainly needed, the following investigation indicates that the standard narrative about the demise of institutional economics after World War II should be amended, 3 and it stimulates interesting questions as to what can be learned for the future of institutional economics.