The studies of Giacomo Becattini concerning the notion of the 'Marshallian Industrial District' have led a revolution in the field of economic development around the world. The paper offers an interpretation of the methodology adopted by Becattini. The roots are clearly Marshallian. Becattini proposes a return to the economy as a complex social science that operates in historical time. The paper is organized in four parts. The first is the introduction and aims. The Becattini?s seminal article of 1979 provides an original interpretation concerning the core of endogenous growth theories: the existence of a mechanism for the creation and transmission of economies external to the firm but internal to the industry. For Becattini, the political economy, the economic analysis in Schumpeterian terms, goes beyond theory and the contrasting of theories. He does not only propose ?a return to the territory?, and a new approach to the area of study concerning industrial analysis, but also a return to the economy as a complex social science that operates in historical time, capable of emphasizing ?social depth? and ?cultural outreach? in empirical research, and of addressing this complex reality together with other disciplines such as history, geography and sociology. The second proposed an interpretation of the Becattini's methodology in the context of the Cambridge School. The links with the Marshall?s method are clears. The method of the economy includes induction, deduction and history, and places the very tools of analysis in their historical context. The third analyses the Becattini's notion of industrial district that is different of the notion proposed by Marshall. Becattinis proposed the term ?Marshallian industrial district? that is only partially accounted for by Alfred Marshall in his Principals of Economics. We will adopt a Robertsonian interpretation of his ideas, stressing the importance of the possibility of increasing manufacturing returns from territories and areas equipped with external economies and small and medium-sized firms. The four part on some relations between the notion of industrial district and the garden city approach, that suggest a relation between this economic notion and the garden city movement, between Alfred Marshall and Ebenezer Howard, between economics and urban planning.