Seeking to deal with the hegemonic discourses that circumscribe land occupations to a legal. criterion, the first section is organized around the weight that informality had in the historical construction of Latin American cities. Taking Commodore Rivadavia as a witness, in the second section the State is dimensioned as a promoter of urban informality. The third section conveys the empirical analysis of the criteria of legitimacy as popular responses to the dominant views of occupations as "illegal acts". Finally, the conclusions propose a revision of the main argumentative lines developed throughout the work.