The Asháninka are known historically to be fiercely independent, and were noted for their "bravery and independence" by the Spanish conquistadors. They resisted with some success missionary endeavors by Roman Catholic missionaries from the 17th to 19th centuries, especially near the Cerro de la Sal (Salt Mountain) amd the Gran Pajonal (Great Grassland) in the central part of the Amazon basin in Peru. During the rubber boom (1839–1913), the Asháninka were enslaved by rubber tappers and an estimated 70% of the Asháninka population was killed.