Political map of South American nations 14 July 1899 (Republic of Acre): During the 1890s, thousands of Brazilian workers traveled up the Amazon to the Bolivian-claimed region of Acre in search of rubber trees - at the time extremely valuable due to the need for rubber in the rising automobile industry (Amazon rubber boom). When Bolivia tried to assert control over the territory, the inhabitants of Acre declared independence (Republic of Acre). Brazil initially supported Bolivian efforts to restore order, but, after further revolts, eventually decided to back the rebels (Acre War). The conflict would end in 1903, when Bolivia finally agreed to cede Acre to Brazil (Treaty of Petropolis).