The political life of XIX century South America was shaped by alternating different constitutional models, each one of them supported by a specific conception of society and of the roles of the individual in them.This article analyzes the perfectionist, collectivist and liberal models, and how they were adopted in the constitutions of different countries of the region.This study makes clear the reasons for the predominance of the liberal model, given the possible excesses of the other two alternatives, without assuming that this implies an uncritical perspective to the said model.