The Guaraní Indians of Paraguay, Argentina and Brazil would just have been another indigenous victim of the colonial conquest in South America, if the Jesuits weren't able to persuade the King of Spain to grant that vast region to their care. They founded several missions or "reducciones" and developed a kind of evangelization a bit peculiar for that time. The first settlement was founded in 1609. The main settlements were along the Rio Paraná along the border of today's Argentina and Paraguay.

Due to the continuous raids of the Paulista slave raiders, the Missions in Brazil were soon abandoned (1640s) and moved to what is now Argentina and Paraguay.
Guided by the Jesuits, the Indios had advanced laws, founded free public services for the poor, schools, hospitals, established birth control, and suppressed the death penalty. All the inhabitants of the reducciones worked in the "tupambae" lands property of the community, and all the products which they produced were fairly divided among them. The Guaraní were very skilled in handicraft works, sculpture, woodcarving etc.; the reducciones, were the first "industrial" state of the South America. Indeed, such advanced products as watches, musical instruments, etc. were produced.

The Missions ended in 1767, with the expulsion of the Jesuits from South America. During that time, the last missions were abandoned and the Indians returned to their forest life.