Tenochtitlan was traditionally founded in 1325. The Mexica established the city on an island in Lake Texcoco, in the Valley of Mexico, after a long migration in search of the site promised by their religious traditions.
According to the foundation story, the Mexica recognized their destined home when they saw an eagle perched on a prickly pear cactus with a serpent in its beak. That image remains a major national symbol of Mexico and appears on the country’s flag and coat of arms.
The exact historical founding date is uncertain because surviving Indigenous and colonial records do not agree perfectly. Nevertheless, 1325 is the conventional date used by historians, museums, and quiz references. The city expanded through causeways, canals, chinampa agriculture, and engineered islands. It became the capital of the Mexica state before being conquered by Spanish and Indigenous allies in 1521.