Due to the disputes by occupation and colonization of the American continent between the crowns of Spain and Portugal, the treaty of tordesillas is signed where driving of both this treaty is delimited never extinguished the expansionistic eagerness of the Portuguese who never respected that treaty. During the time of the Spanish colonization our territory was in virgin state and only inhabited by natives, but closely together of which today they are our borders with the neighboring countries, was based the city of Asuncion from where the Spanish colonizadores, they entered in the today territory of the Province of Misiones, on the other hand the Portuguese colonizadores that were based in the federal Republic today of Brazil, also made incursions, mainly well-known bandeiras (they hunted natives soon to sell them like slaves), this way the zone was throughout that time as a territory in litigation then did not exist establishments of cities on the part of Spaniards nor of Portuguese, single the different reductions existed (founded by the Jesuits). After countries on the part of Paraguay and Brazil develops liberator of the river of the silver approximately stayed in dispute all this territory due to the attempts of incorporation to his (yet Portuguese colony) until year 1830.
In order to make a meticulous detail but of these events, we went back in the time until the foundation of the city of Asuncion in the borders of Paraguay river. A second of Ayolas, Juan de Salazar, founded on the left margin of the Paraguay river the port of Asuncion in August of l537. The site was very good place for an establishment. It surpassed in this sense to the site chosen for the foundation of the port of Buenos Aires. The environs of the port of Asuncion were populated by several populations of guaranies that immediately they related with the Spaniards, having originated themselves a Hispanic-guarani alliance. Some of the chiefs, specially those of the groups of the carios, offered in marriage their daughters to the conquerors. These unions made arise between Spaniards and guaraníes the bows of kinship and the reciprocity in the production and the economy. The Spaniards began to remove good benefit from the institution of cuñadazgo, by which the brothers of the wife had to lend gratuitous work to their brother-in-law. It made arise between the Spaniards the habit of the polygamy, since to more spouses, more lending of work available. The alliance also had a military character: the enemies of the guaraníes, the guaicurúes that inhabited the opposed border of the Paraguay river, also appeared like enemies of the Spaniards. And the Hispanic expansion towards the incaica region, also agreed with the expansion of the guaraníes towards that area, to which they called the kingdom of "Paitití". The establishment prospered with such abundance that in the year l54l the Governing Lieutenant Domingo Martinez de Irala decided the extinction of the port of Buenos Aires and the transfer of everything what it had there, people and equipment, to Asuncion, which was turned city. Asuncion one became an important center of conquest and colonization of the region of the river basin of the Silver. From her they divided expeditions that made a set of foundations that affirmed the Hispanic presence in the region. The foundations were accompanied with explorations of the geography of the region. In the year l542 Alvar Nuñez Cabeza de Vaca crossed on foot all the passage that goes from the island of Santa Catherine, on the Atlantic coast, to the city of Asuncion, making contact with enemy with the guaraníes of the region and discovering the falls of the Iguazú. The harmony of the first moment, product of the unions of Spaniards with guaraníes women, did not take in breaking itself. When I arrive the news that Peru had been conquered by Francisco Pizarro and Diego de Almagro, the illusion of the gold wealth and silver disappeared. Established in a region in which the nature did not offer precious metals, Asuncion, like the other founded cities, had to be dedicated to the agriculture and cattle production. The necessity of manual labor was growing as new cities and the colonization of new earth were based. Then it was begun to apply on the native the regime of the "Encomienda". Groups of guaraníes Indians "were entrusted" to a Spanish or Creole by grace of the Governor and the crown. In the year the entrusted natives had to serve labor to their gentleman during a month. In return the Spanish had to guard by its well-being and to evangelizar to the entrusted native. The regime did not take in degenerating in a brutal oppression, that soon derived in the increase from indigenous mortality and the massive rebellions. By the end of century XVI, the system of "Encomienda" had arrived at the limit from its possibilities, transforming itself into the main factor of annihilation of the native groups and During the years l537 and l606 in 22 indigenous rises. The undertaken punitive expeditions against the native populations caused their massive retirement towards regions like: the region of the Guayrá, the paranaense-uruguayense region and the one of Tape', to the east of the Uruguay river.