The historical roots of macroeconometric model building go back to the studies of Jan Tinbergen in constructing statistical models of The Netherlands and the United States. His work built on the contributions of J.M. Keynes to macroeconomic theory and Simon Kuznets to the design of accounts to measure national income and product. Wassily Leontief's input-output models helped to extend the effort to many industrial sectors. Other economic theorists and statisticians also made important contributions in the 1930s and 1940s. A breakthrough has been the arrival of the electronic computer. Many seemingly impossible tasks are now quite easy. Among the many approaches to economic forecasting, policy analysis, and cyclical analysis, macroeconometric modeling stands out as the most accurate and insightful. There are many challengers, but none that is demonstrably superior on a replicated basis. The present thrust of model building has extended beyond Professor Tinbergen's original work at the national level. World models of economic interdependence are now operational in many international centers.