The focal point of this article is the construction of the moveable and complex territorial matrix upon which Argentinian cities and towns have been built. For this reason, the direction of city/territory analysis has been inverted in order to study the territory/city axis. Our question is: what was the role of the Federal government in regulating territorial delimitations? Within this frame, which includes the contemplation of boundaries as constitutive elements of the problem, I will discuss the incidence of the emerging jurisdictional structures political and legal in the construction of the modern territory and the founding of cities in the mid-nineteen and early twentieth centuries. The analysis is based on the province of Buenos Aires, a space considered to be a laboratory and pioneer in the first experiences that would later extend to the rest of the country with the new national territories created in the expansion of the frontier.