Founding of Tenochtitlan (1325): Birth of the Aztec Capital

The founding of Tenochtitlan, traditionally dated to 1325, was the moment when the Mexica people settled on a small marshy island in Lake Texcoco, in the Valley of Mexico. According to their own tradition, they stopped there after a long migration when they saw an eagle perched on a cactus, the sign promised by their god Huitzilopochtli. Within two centuries the settlement had become the capital of the Aztec Empire and one of the largest cities in the world.

Background: the Valley of Mexico around 1300

The Valley of Mexico is a high basin, more than 2,200 m above sea level, ringed by mountains. In the 14th century its floor was largely covered by a chain of shallow lakes, of which Lake Texcoco was the largest. Its shores were densely settled by city-states, many claiming descent from the prestige of the earlier Toltecs of Tula.

The most powerful of these states was Azcapotzalco, ruled by the Tepanecs on the western shore. Others included Culhuacan, Texcoco, Xochimilco and Chalco. All competed for land, water and tribute, and new arrivals had to find a place among them.

The migration from Aztlan

The Mexica told their history in painted books and oral traditions, later recorded by Spanish friars and by Indigenous and mestizo historians in the 16th century. These accounts say that the Mexica came from a place called Aztlan, “place of the herons” or “place of whiteness”, somewhere to the north-west. The name “Aztec” derives from Aztlan, although the people called themselves Mexica.

Guided by priests who carried the image of their patron god Huitzilopochtli, the Mexica wandered for generations. Traditions describe a stay at Coatepec, the “serpent hill”, where Huitzilopochtli was said to have been born and to have defeated his sister Coyolxauhqui and his four hundred brothers. This myth would later shape the design of the city’s Great Temple.

Historians debate how much of the migration story is literal history. The location of Aztlan has never been identified, and the narrative contains clear religious and political elements. Most agree, however, that the Mexica were among the last of several groups of Nahuatl-speaking migrants who entered central Mexico from the north between the 12th and 14th centuries.

Chapultepec and Culhuacan

When the Mexica reached the Valley of Mexico, they first settled on the hill of Chapultepec, near the western shore of the lake. Their neighbours saw them as dangerous newcomers, and around the early 14th century a coalition attacked and drove them out. Their leader, Huitzilihuitl the Elder, was captured and killed.

The survivors became dependants of Culhuacan, which allowed them to live on barren, snake-infested land at Tizaapan. According to tradition the Mexica thrived there, even eating the snakes, and served Culhuacan as mercenaries.

A famous and grim story explains why they left. The Mexica asked the ruler of Culhuacan for his daughter, promising to honour her as a goddess. Instead, the story says, they sacrificed her, and when her father saw a priest dressed in her flayed skin at a ceremony, the Culhua drove the Mexica into the marshes of the lake. Whether or not this event happened as told, it became part of the Mexica account of how they reached their final home.

The eagle on the cactus

Fleeing into the reeds, the Mexica reached a group of small islands in the western part of Lake Texcoco. There, the tradition says, they saw the sign Huitzilopochtli had promised: an eagle perched on a nopal (prickly pear) cactus growing from a rock. In many versions the eagle is devouring a snake, though the snake is absent or replaced by other symbols in some early sources.

The name Tenochtitlan is usually translated as “place of the prickly pear cactus on the rock”, from the Nahuatl words for stone and prickly pear. It is also linked to Tenoch, the leader the sources credit with guiding the Mexica at the founding. The first page of history in the Codex Mendoza, painted around 1541, shows the eagle on the cactus at the centre of the city, surrounded by ten founding leaders, with Tenoch prominent among them.

The date given in the Codex Mendoza is the year 2 House, which corresponds to 1325. Other sources give years from around 1321 to 1345. Because the year 2 House also had symbolic importance in Mexica calendars, many scholars treat 1325 as a traditional rather than precise date. Archaeological work beneath Mexico City confirms occupation of the island in the 14th century, but cannot pin down a founding year.

Building a city on water

The first Tenochtitlan was a modest settlement of reed and mud huts around a small shrine to Huitzilopochtli. The Mexica lived from the lake, catching fish, waterfowl and insects, gathering algae and trading these goods with lakeshore towns for stone and timber.

Around 1337, according to tradition, a dissident group split away and founded Tlatelolco on a neighbouring island to the north. The two cities remained rivals until Tenochtitlan conquered Tlatelolco in 1473.

The key to the city’s growth was the chinampa, a raised garden plot built up from layers of mud and vegetation and anchored by willow trees. Chinampas created rich farmland on the lake and gave the city its grid of canals. Over time, causeways linked the island to the mainland: to Tepeyac in the north, Tlacopan in the west and Iztapalapa and Coyoacan in the south.

For its first century the city was politically subordinate. The Mexica paid tribute to the Tepanec rulers of Azcapotzalco, especially under the long-reigning king Tezozomoc, and fought as their mercenaries. In about 1375 they installed their first recognised king (tlatoani), Acamapichtli, who had royal Culhua and Toltec-linked ancestry, strengthening their legitimacy.

From island town to imperial capital

The turning point came in 1428, when Tenochtitlan joined Texcoco and Tlacopan to defeat Azcapotzalco, forming the Aztec Triple Alliance. Tribute from conquered provinces now flowed into the city.

Successive rulers enlarged the ceremonial precinct and rebuilt the Templo Mayor, the twin-shrined pyramid at the city’s heart, many times. After a disastrous flood in 1449, Nezahualcoyotl of Texcoco helped design a long dike that separated the brackish eastern lake from the fresher waters around the city. A stone aqueduct carried spring water from Chapultepec.

When Spanish soldiers entered the city in November 1519, they were astonished by its size, its markets and its causeways. By then Tenochtitlan probably covered around 13–15 square kilometres. Population estimates usually range from 150,000 to 250,000, with some scholars proposing lower or higher figures.

How historians know the story

Almost everything known about the founding comes from sources written after the Spanish conquest. Some, such as the Codex Mendoza and the Codex Boturini, the latter also called the Tira de la Peregrinación, preserve painted histories in Indigenous style. Others are prose chronicles by Spanish friars such as Diego Duran and Bernardino de Sahagun, and by writers of Nahua descent such as Hernando Alvarado Tezozomoc and Chimalpahin.

These sources agree on the outline but differ on names, dates and details, and each reflects the interests of particular cities and families. Historians therefore combine them with archaeology, which shows the gradual growth of the island settlements, to reconstruct a likely picture.

Legacy

Tenochtitlan fell to Hernan Cortes and his Indigenous allies in the Fall of Tenochtitlan in August 1521, after a long siege. The Spanish built Mexico City on its ruins, filling in canals and reusing temple stones for churches and palaces. Over the following centuries the lakes were largely drained.

The founding legend did not disappear. The eagle on the cactus became a symbol of Mexico, and since independence in the 19th century it has stood at the centre of the Mexican flag and coat of arms. Excavations in the historic centre since 1978 have revealed the remains of the Great Temple and many other structures of the old city.

Myths and facts

• Myth: the Aztecs called themselves Aztecs. The people of Tenochtitlan called themselves Mexica, or Tenochca. “Aztec” was popularised by 18th- and 19th-century writers, drawing on the name of Aztlan.
• Myth: the city was founded on solid land. The original site was a cluster of low, swampy islets. Much of the later city’s land was created artificially by filling in the lake and building chinampas.
• Myth: the founding date is precisely known. 1325 is the traditional date, but sources disagree, and the year had symbolic value in the Mexica calendar.

Timeline

• 12th–13th centuries: Nahuatl-speaking groups, including the Mexica, migrate into central Mexico.
• Early 14th century: The Mexica are driven from Chapultepec and become dependants of Culhuacan.
• 1325 (traditional): Founding of Tenochtitlan on an island in Lake Texcoco.
• c. 1337 (traditional): Founding of Tlatelolco on a neighbouring island.
• c. 1375: Acamapichtli becomes the first tlatoani of Tenochtitlan.
• 1428: Defeat of Azcapotzalco; the Triple Alliance is formed.
• 1473: Tenochtitlan conquers Tlatelolco.
• 1519, November: Spanish forces enter Tenochtitlan.
• 1521, August: Tenochtitlan falls after a long siege.

Why it matters

The founding of Tenochtitlan began the story of the most powerful state in Mesoamerica at the time of European contact. Its legend shaped Aztec religion and politics and survives in Mexico’s national symbols. The city itself, built on water with remarkable engineering, remains the foundation, literally, of one of the largest cities in the modern world.