This article confronts three persistent problems in the analysis of the U.S. urban system by (a) employing a continuous, rather than a discrete, classification scheme that (b) has been replicated successfully for three time periods to (c) describe regional variations and changes in the U.S. metropolitan system from 1950 to 1970. Two fundamental dimensions describe the system in 1950, 1960, and 1970; an industry structure (manufacturing-service) continuum and a financial-commercial hierarchy. Familiar regional variations in the structure of metropolitan areas are summarized by these dimensions. Unique to this analysis is a description of clear regional changes in the metropolitan system from 1950 to 1970. Northeastern SMSAs became more service oriented, North Central SMSAs became more manufacturing oriented and less financially dominant, and Southern SMSAs increased dramatically in their degree of financial-commercial dominance. Theoretical interpretations of these regional shifts are discussed.
