[1] The design is rooted in the legend that the Aztec people would know where to build their city once they saw an eagle eating a snake on top of a lake.

The seal differs from the arms by the addition of the words Estados Unidos Mexicanos ("United Mexican States", the full official name of the country) in a semicircle around the upper half.

The cactus (Opuntia ficus-indica), full of its fruits, called nōchtli in Nahuatl, represents the island of Tenochtitlan.

The story of the snake was derived from an incorrect translation of the Crónica Mexicáyotl by Fernando Alvarado Tezozómoc.

Although this interpretation does not conform to pre-Columbian traditions, it was an element that could be used by the first missionaries for the purposes of evangelism and the conversion of the native peoples.

[3] In 1960, the Mexican ornithologist Rafael Martín del Campo identified the eagle in the pre-Hispanic codex as the crested caracara or "quebrantahuesos" (bonebreaker), a species common in Mexico (although the name "eagle" is taxonomically incorrect, as the caracara is in the falcon family).