What three city-states formed the Aztec Triple Alliance?

The Aztec Triple Alliance consisted of Tenochtitlan, Texcoco, and Tlacopan. Formed in 1428 after the defeat of the Tepanec power Azcapotzalco, the alliance became the political and military foundation of what historians commonly call the Aztec Empire.

The three city-states were independent Nahua polities rather than three neighborhoods of one unified city. They agreed to cooperate in warfare and divide the spoils and tribute gained from conquest. Tenochtitlan and Texcoco each received two-fifths of the tribute, while Tlacopan received one-fifth, reflecting its position as the alliance’s junior partner.

Over time, Tenochtitlan became the dominant member, controlling much of the alliance’s military expansion and serving as its de facto center. Texcoco was also renowned for scholarship, law, architecture, and the rule of the poet-king Nezahualcoyotl. The alliance lasted until 1521, when the Spanish and their Indigenous allies captured Tenochtitlan. Azcapotzalco, Chalco, Tlatelolco, and Culhuacan were important regional powers, but they were not members of the original Triple Alliance.