We explore disciplinary boundary-making in geographical economics or “the new economic geography” with attention to the approaches taken by, and attempts at communication among, scholars with primary affiliations in economics, geography, and regional science. The Dixit-Stiglitz general equilibrium approach to monopolistic competition and increasing returns was applied to agglomeration and location by Paul Krugman, who had previously pioneered the “new trade theory” building on the Dixit-Stiglitz model, and, independently and slightly earlier, by Masahisa Fujita and his student Heshem Abdel-Rahman, starting from regional science, a tradition with its own departments, doctorates, conferences, and journals distinct from economics and geography. Economic geography, as studied by geographers, had already taken a quantitative and theoretical turn in the 1960s, reviving an earlier tradition of German location theory overshadowed within geography after World War II by areal differentiation. Another strand of economic geography pursued by geographers was influenced by economic theory but by non-neoclassical Marxian and Sraffian economics. Debates between these scholars raised questions whether these analyses were multidisciplinary, drawing on distinct disciplines, or crossed disciplinary boundaries (as when geographical economics in the style of economists is undertaken in geography departments) or transcends disciplinary boundaries, or involved the emergence of a new discipline.