This paper outlines the contributions of J.M. Clark to institutional economics. Clark is sometimes seen as standing between institutional and neoclassical economics, but I argue that this view is not accurate. Clark was intimately involved in the definition, promotion, and defense of institutional economics in sessions of the American Economic Association and in a variety of other forums. No other member of the institutionalist group was as much involved in the professional discussion of institutional economics as J.M. Clark. In addition, Clark made a number of key contributions to institutionalist theory in the areas of psychology and economics, the costs of decision-making, overhead costs and business-pricing behavior, the accelerator mechanism and business cycles, workable and effective competition and competition policy, and social control. These contributions, together with the graduate students he trained at the University of Chicago and Columbia University, serve to place him in the center of the institutionalist movement and not on its periphery.
