At the end of the XIXth century, the demand for car tires was very high and triggered a rush for rubber in the entire world. The resources in the north of Bolivia massively attracted Brazilians workers in this area which was under-populated and poorly controlled by Bolivia. The raw rubber material was conveyed by river (e.g. the Amazon) to the Brazilian harbor of Manao before being exported to the USA and Europe.
In May 1899, the Brazilian settlers, supported by their government, declared the independence of the Acre, territory located at the North-East of Bolivia. The Bolivian army intervened, but the superiority of the opponents as well as the hostile Amazonian geography turned to the advantage of the Brazilians. After hard combat, Bolivia was forced to give up the conflict and signed the treaty of Petrˇpolis (Brazil) on November 17, 1903, losing the whole Acre territory. A financial compensation was provided by Brazil as well as its engagement to build a railroad connecting the two countries in order to increase trade.