The Amazon Basin is the part of South America drained by the Amazon River and its tributaries. The basin is located mainly (54%) in Brazil, but also stretches into Peru and several other countries. The South American rain forest of the Amazon is the largest in the world, covering about 8,235,430 km2 with dense tropical forest. For centuries, this has protected the area and the animals residing in it.
Upon the European discovery of America, the Portuguese and the Spanish signed the Treaty of Tordesillas, dividing the country into a large Spanish western part, which encompassed all of the then unknown North America and Central America, and western South America, the Portuguese had Eastern South America, what would become modern eastern Brazil. The Spanish claim was confirmed by explorers, most famously by the expedition of Francisco de Orellana in 1541-42.
By the late 17th century Portuguese/Brazilian explorers had dominated much of the Amazon basin because the mouth of the Amazon river lay within the Portuguese side, and the Brazilian inward exploration venturers such as the Bandeirantes, who originated in São Paulo, had conquered much of what is today central Brazil (states of Mato Grosso, Mato Grosso do Sul, Goiás) and then proceeded to the Amazon. In 1750 the Treaty of Madrid certified the transfer of most of the Amazon basin and the region of Mato Grosso to the Portuguese side, hugely contributing to the continental size of what is now Brazil.
In 1903 Brazil bought a large portion of northern Bolivia and made it its current state of Acre. In 2006 the new socialist Bolivian president Evo Morales talked about "getting it back. The Brazilians got it for the price of a horse". No action was taken and the two nations remain friendly. In the late 19th century, a US-Brazilian joint venture failed to implement the Madeira-Mamoré railway, in the state of Rondônia, with a huge cost in money and lives.
Intense deforestation began in the second half of the 20th century, with population growth and development plans such as the failed Brazilian Trans-Amazonian Highway. In the late 1980s the Brazilian Chico Mendes, who lived in Acre, became internationally famous for his passionate defense of the forest and its people, especially after he was shot to death by farmers whose interests he harmed.
There are hundreds of native languages still spoken in the Amazon, most of which are spoken by only a handful of people, and thus seriously endangered. One of the most widely spoken languages in the Amazon is Reengage, which is actually descended from the ancient Tupi language, originally spoken in coastal and central regions of Brazil, and brought to its present location along the Rio Negro by Brazilian colonizers, who until the mid-17th century used Tupi more than the official Portuguese to communicate. Besides modern Reengage, other languages of the Tupi Family are spoken there, along with other language families like Jê (with its important subbranch Jayapura spoken in the Xingu River region and others), Arawak, Karib, Arawá, Yanomamo, Matsés and others. French, Spanish, and Portuguese are all similar to and derived from Latin.