This paper proposes a methodology to calculate the systemic risk in historical research, understanding that the characteristics of non modern financial systems and the availability of information do not enable the use of recent techniques of measuring financial risk. I propose a method of simple application and scarce information requirements, using the degree of leverage as an approximation of the individual risk, and the network theory to determine the allocation of individual risks throughout the system. The methodology is especially useful for studying the banking systems in early corporatizing periods. After been exposed the methodology, which takes as its central axis the shareholders, and the property as base linkages between institutions, it is mentioned its strengths and weaknesses; being, finally, tested in an application for the free banking experience in Antioquia.