Multiple verbal and pictorial sources give an account of the origins of the Mexica and that narrate the process through which these people went through until the foundation of Mexico-Tenochtitlan. However, one of the most significant is the Codex Boturini, since it is a manuscript that legibly records the departure of the Mexica from their ancient land until they arrived in the Valley of Mexico a few years before Tenochtitlan was erected.

Although this file is unfinished, it is considered one of the foundational documents of the history of our country, since it is the earliest document of the Aztec migration and the historical version it portrays is one of the most widely used. It is even reproduced in large dimensions in the central courtyard of the National Museum of Anthropology. The codex, also known as the Pilgrimage Strip, was made on a strip of amate made up of 22 sheets that form a screen of 5.49 meters. It is believed that it may be based on or a copy of an older document.

According to what is narrated in the plates, the god Huitzilopochtli orders the Aztecs to abandon Aztlan, their land of origin whose name means "place of herons" or "place of whiteness", a mysterious site located to the north that probably gets its name from the abundance of herons in the waters surrounding the island where this people originally settled.

Their god tells them to look for a new settlement, so the Aztecs, carrying the relics or a wooden figure representing Huitzilopochtli, begin their journey through desert places accompanied by seven or eight barrios from a nearby village. After separating from them by order of their god, they encountered on their way the mimixcoas, lunar divinities, or demons. Huitzilopochtli ordered the Aztecs to sacrifice them as a first offering to him. After the sacrifice, Huitzilopochtli renamed his people and from that moment on they took the name of Mexica; they were thus consecrated when their god gave them the bow, arrow, and net.

They continued on their way and settled for the first time since leaving Aztlan in Coatlicamac (the jaws of the serpent) and Cuextecaichocayan (the place where the Huastec cried). The codex narrates that after several decades they arrived at Tollan, where they stayed for 20 years, to later arrive at the ancient lake of Texcoco, where they traveled and settled in different areas for several years (Tlemaco, Atotonilco, Apazco, Tzompanco, Xaltocan, Acalhuacan, Ehecatepetl, Tulpetlac and Cohuatitlan, in the latter they discovered the maguey and learned to make pulque).

They are attacked by a village and forced to settle in Pantitlan, where they are victims of an epidemic.

They continued their nomadic journey until they settled in Chapultepec for 20 years, but there they are taken prisoner by the tlatoani of Colhuacan, who, given the abundance of Mexica in one of his neighborhoods, uses them as warriors to get rid of them in a battle against the Xochimelcas. The tlatoani asks them to kill or take prisoner several of them and to cut off their ears, which they must carry in a sack as a token of their feat. The Mexica organize themselves and decide to use obsidian blades as weapons and resolve that they will cut off the noses of their enemies so that the tlatoani of Colhuacan does not think that they cut off both ears; thus they will carry one piece for each enemy.

This is the point of the Codex Boturini, which relates the vicissitudes of these people before the encounter with the sacred manifestation of the eagle over the tunal, a vision narrated as a prophecy dictated by Huitzilopochtli as a sign of the place chosen to settle. From this moment the definitive sedentary period of the Mexica begins; the portent of the eagle and the nopal is narrated in the Codex Mendocino, in which it is shown among other characters Tenoch, a priest seated on a petate that glimpses the eagle where Tenochtitlan is founded (the place near the tunal).

There is no consensus on the date of its foundation; however, at the beginning of the 20th century, March 13, 1325, was designated as the date for the commemoration of the founding of Tenochtitlan.