Standardized features dominate the retail landscape of the United States and are the physical components of retail districts. This study tests the hypothesis that standardized building blocks have failed to produce the same retail structure in all metropolitan statistical areas (MSAs). Ninety-two medium-sized MS As are analyzed to determine if the arrangement and strength of their retail districts differ. The relationship between functional and spatial aspects of retail structure in central place theory provides a basis for testing the hypothesis of diversity. Christaller's separation principle provides a plausible conceptual framework for diverse retail structure if each MSA is analyzed as an isolated region. Five types of retail structure are analyzed using data obtained from the Census of Population and the Census of Retail Trade. The types are identified by performing a serial iterative partition cluster procedure on prioritized metropolitan sales variables. The statistical significance of the types is tested with Mann-Whitney U-tests of functional variables not used in the cluster analysis. Verification confirms five distinctive types. Monocentric and polycentric retail structures exist but decentralized retail structure is even more common in medium-sized MSAs. The distribution of types of retail structure follows regional pattern that indicate historical and political factors as contributing causes.