Quiroga, Juan Facundo (hwän fäkōnˈħō kērōˈgä) [key], 1790–1835, Argentine caudillo. One of the most brutal of the early gaucho chieftains, he was called el tigre de los llanos (the tiger of the plains). After a turbulent youth, Quiroga participated briefly in the 1810 revolution against Spain and then rose rapidly to become, by 1822, virtual overlord of the Andean provinces of Argentina. Anxious to preserve control over his fiefdoms, he became a supporter of federalism. With other provincial caudillos he rejected the unitarian constitution of 1826, thus contributing to the downfall of President Bernardino Rivadavia and to the installation (1827) of Manuel Dorrego, a federalist, as governor of Buenos Aires. When Juan Lavalle rose against Dorrego and had him executed, Quiroga and Juan Manuel de Rosas joined Estanislao López, caudillo of Santa Fe, in putting down the insurrection and in destroying temporarily but with ruthless thoroughness the unitarian cause. In 1834, Quiroga came to Buenos Aires, which was then ruled by Rosas. Quiroga was assassinated while returning from a mission to the northern provinces, and it was believed that Rosas, who was angered by the rival caudillo, had instigated the killing. A famous study of Quiroga and his era is Domingo F. Sarmiento's Facundo (tr. Life in the Argentine Republic in the Days of the Tyrants, 6th ed. 1961).