The only pre-Columbian North American rulers to be commonly called emperors were the "Hueyi Tlatoani" of the Aztec Empire (1375–1521). It was an elected monarchy chosen by the elite. In the Aztec Empire, there were three emperors: Those of Tenochtitlan, Tlacopan and Texcoco. The Emperors of Tenochtitlan and Texcoco were nominally equals, each receiving two-fifths of tribute from the vassal kingdoms, whereas the Emperor of Tlacopan was a junior member and only received one-fifth of the tribute, due to the fact that Tlacopan was a newcomer to the alliance. Despite the nominal equality, Tenochtitlan eventually assumed a de facto dominant role in the Empire, to the point that even the Emperors of Tlacopan and Texcoco would acknowledge Tenochtitlan's effective supremacy. Spanish conquistador Hernán Cortés slew Emperor Cuauhtémoc and installed puppet rulers who became vassals for Spain.