The homeland of the Uto-Aztecan languages is generally considered to have been in the Southwestern United States or possibly Northwestern Mexico.

In Mexico, they are spoken in the states of Sonora, Sinaloa, Chihuahua, Nayarit, Durango, Zacatecas, Jalisco, Michoacán, Guerrero, San Luis Potosí, Hidalgo, Puebla, Veracruz, Morelos, Estado de México, and in Mexico City.

The Pipil language, an offshoot of Nahuatl, spread to Central America by a wave of migration from Mexico, and formerly had many speakers there.

The similarities among the Uto-Aztecan languages were noted as early as 1859 by J. C. E. Buschmann, but he failed to recognize the genetic affiliation between the Aztecan branch and the rest.

Daniel Garrison Brinton added the Aztecan languages to the family in 1891 and coined the term Uto-Aztecan.

John Wesley Powell, however, rejected the claim in his own classification of North American indigenous languages (also published in 1891).

[8][9][10] Sapir's applications of the comparative method to unwritten Native American languages are regarded as groundbreaking.

Northern Uto-Aztecan was proposed as a genetic grouping by Jeffrey Heath in Heath (1978) based on morphological evidence, and Alexis Manaster Ramer in Manaster Ramer (1992) adduced phonological evidence in the form of a sound law.

[12][13][14][15] Wick R. Miller's argument was statistical, arguing that Northern Uto-Aztecan languages displayed too few cognates to be considered a unit.

On the other hands he found the number of cognates among Southern Uto-Aztecan languages to suggest a genetic relation.

The classification reflects the decision to split up the previous Taracahitic and Takic groups, that are no longer considered to be valid genetic units.