Tetzcoco (Classical Nahuatl: Tetzco(h)co tetsˈkoʔko) was a major Acolhua altepetl (city-state) in the central Mexican plateau region of Mesoamerica during the Late Postclassic period of pre-Columbian Mesoamerican chronology. It was situated on the eastern bank of Lake Texcoco in the Valley of Mexico, to the northeast of the Aztec capital, Tenochtitlan. The site of pre-Columbian Tetzcoco is now subsumed by the modern Mexican municipio of Texcoco and its major settlement, the city formally known as Texcoco de Mora. It also lies within the greater metropolitan area of Mexico City. Pre-Columbian Tetzcoco is most noted for its membership in the Aztec Triple Alliance. At the time of the Spanish conquest of the Aztec Empire, it was one of the largest and most prestigious cities in central Mexico, second only to the Aztec capital, Tenochtitlan. A survey of Mesoamerican cities estimated that pre-conquest Tetzcoco had a population of 24,000+ and occupied an area of 450 hectares. The people of Tetzcohco were called Tetzcocatl tet͡sˈkokat͡ɬ (singular) or Tetzcocah tet͡sˈkokaʔ (plural). Tetzcoco was founded in the 12th century, on the eastern shore of Lake Texcoco, probably by the Chichimecs. In or about 1337, the Acolhua, with Tepanec help, expelled Chichimecs from Tetzcoco and Tetzcoco became the Acolhua capital city, taking over that role from Coatlinchan. In 1418, Ixtlilxochitl I, the tlatoani (ruler) of Tetzcoco, was dethroned by Tezozomoc of Azcapotzalco. Ten years later, in 1428, Ixtlilxochitl's son, Nezahualcoyotl alliedLeón-Portilla, M. 1992, 'The Broken Spears: The Aztec Accounts of the Conquest of Mexico. Boston: Beacon Press, with the Mexica to defeat Tezozomoc's son and successor, Maxtla. Tetzcoco and the Aztecs of Tenochtitlan, with the Tepanecs of Tlacopan, subsequently formalized their association as the Triple Alliance. However this was an uneven alliance as Tlacopan entered the battle against Azcapotzalco late.