The Conquest of the Río de la Plata is a particular case within the Spanish Empire : beyond an inner boundary established by the conquerors – the indian frontier – the Natives maintained control over their territory, as well as they did facing the british colonies in North America. During four centuries, two societies thus coexisted on both sides of this theoretical and movable line, a space of conflicts, but of intense and continuing exchanges too. This doctoral thesis intend to study the inner South-West Frontier, from the first contacts with the indigenous peoples in the 16th century until the militarycampaigns carried out by the government of Argentina at the end of the 19th century and making it disappear, as well as in the United States. The study will give the opportunity to review the changings in this border space, first during the colonial period, then at the time of the Independence wars, and finally the various processes which will lead to the abolition of this frontier, as well as of independent amerindian tribes during the 19th century
