Río Biobío
La Frontera is a name used in Chile to refer to the region around the Bío Bío River, or to the whole area between there and the Toltén River. The use of this latter definition is largely coterminous with the historical usage of Araucanía. The term was coined during the period when the region was the frontier of the Captaincy General of Chile, then a part of the Spanish Empire and later the Republic of Chile, with the Mapuche people inhabiting the Araucanía following their revolt in 1598. Subsequently, the Spanish Empire established a system of forts between the Bío Bío River and the Itata River, as well as some within the Araucanía. This system continued through the 18th century and into the 19th century.