Abstract: US economic activity is overwhelmingly concentrated at its ocean and Great Lakes coasts, reflecting a large contribution from coastal proximity to productivity and quality of life. Extensively controlling for correlated natural attributes and initial conditions decisively rejects that the coastal concentration of economic activity is spurious or just derives from historical forces long since dissipated. Measuring proximity based on coastal attributes that contribute to either productivity or quality of life, but not to both, suggests that the coastal concentration derives primarily from a productivity effect but also, increasingly, from a quality of life effect. Copyright 2003 by Kluwer Academic Publishers