European exploration and penetration of South America started at the beginning of the 16th cent. Under the Treaty of Tordesillas, Portugal claimed what is now Brazil, and Spanish claims were established throughout the rest of the continent with the exception of Guyana, Suriname, and French Guiana. An Iberian culture and Roman Catholicism were early New World transplants—as were coffee, sugarcane, and wheat. The subjugation of the indigenous civilizations was a ruthless accompaniment to settlement efforts, particularly those of Spain. The Inca Empire, centered at Cuzco, Peru, was conquered (1531–35) by Francisco Pizarro; other native cultures quickly declined or retreated in the face of conquest, conversion attempts, and subjugation. Spain and Portugal maintained their colonies in South America until the first quarter of the 19th cent., when successful revolutions resulted in the creation of independent states.
The liberated countries generally struggled with political instability, with revolutions and military dictatorships common and economic development hindered. Between 1820 and 1920, the continent received almost 6 million immigrants, nearly all from Europe. Guyana gained independence from Great Britain in 1966 and Suriname from the Netherlands in 1975. French Guiana is an overseas department of France.
Beginning in the 1970s, road building and the clearing of land led to the destruction of large areas of the Amazonian rain forests. International pressure and changes in government policy, especially in Brazil, resulted in a decrease in the deforestation rate since the late 1980s, although burning and illegal logging continue. Efforts to combat the illegal drug trade have been largely ineffective. Peru is one of the world's largest growers of coca leaves, and Colombia is a center for the drug trade.
Economic problems and social inequality have led to considerable unrest and political instability. Many indigenous peoples, angered by centuries of domination by a primarily European-descended upper class, have demanded a more equal distribution of land and power. Despite the increasing industrialization of some countries, notably Brazil, Venezuela, and Argentina, and the widespread introduction of free-market reforms in the 1990s, high inflation and huge foreign debt continued to be major problems for many South American countries. Such economic problems led to a rise in populist political parties and movements in the region in the early 21st cent., most notably in Venezuela and Bolivia.