This degree of geographic concentration of individual manufacturing industries in the U.S. has declined only slightly in the last twenty years. At the same time, new plant births, plant expansions, contractions and closures have shifted large quantities of employment across plants, firms and...

This paper discusses the prevalence of Silicon Valley-style localizations of individual manufacturing industries in the United States. A model in which localized industry-specific spillovers, natural advantages, and random chance contribute to geographic concentration motivates new indices of...