Historically speaking, the Mapuche people is native to the central and southern area of Chile (present-day regions of Araucanía, Bíobío, Los Ríos and Los Lagos). Before the arrival of the Spaniards there is evidence that the Mapuche crossed the Andean Cordillera to the Patagonian plains (present-day Argentina) and established close and fluid relations with the Puelche (in Mapudungu, "eastern people"), that is, trans-Andean native societies (such as the Tehuelche, the Huarpe and the so-called "ancient pampas" or "Het" peoples). However, it was not until the 16th century that the process of expansion of their culture, influence and language begun into what they called the Puel Mapu (in Mapudungu, "eastern land"). Driven mostly by the terrible consequences suffered in the aftermath of the Arauco War (1536-1818), but also fostered by the rich resources found in the plains, Mapuche migrated to Patagonia and settled in the present-day provinces of Chubut, Río Negro and Neuquén, before expanding into the phyto-geographical region known as "pampa": south of Mendoza and Córdoba provinces, La Pampa province and some parts of the provinces of Buenos Aires, Santa Fe and San Luis.
The expansion lasted until 1850 and it is known as the "araucanization" o "mapuchization of the Pampa". In many cases the process entailed either the fusion with native peoples, while in many others it involved their military defeat, cultural assimilation or annihilation.
Among the first Mapuche to arrive in Argentina there were those who, probably in pre-Hispanic times, gradually merged with the southern Huarpe communities of the provinces of Mendoza and Neuquén, and from whom "Pehuenche" (from Mapudungu pewenche, "people of the pehuenes") would have descended. Much later, historical chronicles record the arrival of an ethnic group known as the "Voroga", native to the Chilean province of Cautín. They were warriors who had fought on the side of the Spanish king Ferdinand VII and, after the defeat of the Spanish "realistas" (the King’s followers) in Chile during the Independence War (towards 1816), moved to Argentina. They carried out cattle raids and looting ("malones") on the Pampa region of Argentina and ended up displacing its ancient inhabitants the "Het", before settling down in the west of the province of Buenos Aires. In 1834 the Voroga were massacred by Huilliche warriors under the leadership of the longko Kallfükura (Calfucurá, in Mapudungu "blue stone"), who dominated the northern Pampa from that moment to the so-called "Conquest of the Desert" (1869-1888), a military campaign under the leadership of Julio Argentino Roca which involved the genocide of indigenous populations.
Towards 1821, after defeating the Gününa-küna (northern Tehuelche) in Choele Choel (present-day province of Río Negro), a Mapuche group controlled the northern border of Patagonia as well as the southern Pampa plains. Both Patagonia and Pampa regions were subject to a variety of cultural influences undergoing processes of racial admixture, fusions and divisions that make it difficult to trace back Argentinean Mapuche history. Such terms as "pampas", "ranqueles", "puelches" "pehuenches", "serranos", "salineros" or "manzaneros" populate Argentinean history book pages despite the changing and sometimes ephemeral borders of the societies named by them.
Mapuches brought their own traditions into Argentina such as the Mapudungu language (which in the Pampa region would place a peculiar stress on the last syllable of the word); their beliefs and religious ceremonies (including the ngillatun); their musical instruments; their traditional attire (which replaced the quillango, a blanket made of sewn guanaco skins); as well as their silverwork, ceramics and textiles, while adopting those cultural features of the peoples native to this region that make it easier for them to live in their territory: the use of "toldos" (tents made of animals skins) instead of their traditional rukas, and the boleadoras (throwing weapons made of weights on the ends of interconnected leather cords) used as hunting and war tools.
Nowadays, over 100,000 Mapuches live in Argentina, mostly in the provinces of La Pampa, Buenos Aires, Neuquén, Río Negro and Chubut. These groups are highly acculturated but have started a process of language and cultural traditions recovery.
Mapuche, in Wikipedia.
Araucanization of Patagonia, in Wikipedia.
Arauco War, in Wikipedia.
Confederación boroana, Argentina (Boroano people), in Wikipedia [es].
Conquest of the Desert, in Wikipedia.
Ranquel people, in Wikipedia.
Pampa (ethnic group), in Wikipedia [es].
Article. "Características de la araucanización al oriente de los Andes", by Rodolfo Casamiquela. In Catholic University of Temuco [es].
Article. "Muestra Virtual Poblamiento Pampeano", in Provincial Historical Archive of La Pampa [es].