Nicolás Avellaneda (nēkōläs´ ävāyänā´ŧħä), 1837–85, Argentine statesman, president of the republic (1874–80). As minister of justice, religion, and public instruction under Domingo F. Sarmiento (1868–74), he introduced many banking and educational reforms. After his election as president, he suppressed a revolt led by Bartolomé Mitre, the defeated candidate. His administration was notable for economic growth and for the conquest of the Native American frontier southwest of Buenos Aires. An expedition under Gen. Julio A. Roca (1878–79) drove the Native Americans beyond the Río Negro, opening the territory of Patagonia for colonization. Much of the new land, however, went in large tracts to speculators, influential politicians, and the great landowners. Avellaneda was chiefly responsible for the plan, approved in 1880, by which the city of Buenos Aires was federalized, thereby settling the political tensions that had long existed between the city and Buenos Aires prov.