Western Mexico includes the modern states of Sinaloa, Nayarit, Jalisco, Colima, Michoacán, parts of Guanajuato, and Guerrero. During the Formative Period (1800 BCE – 200 CE), cultures such as Capacha (Colima), El Opeño (Michoacán), Chipícuaro (Guanajuato), and San Jerónimo (Guerrero) flourished, alongside early Olmec influences.

From 200 to 900 CE, the region saw the rise of the shaft tomb tradition in Jalisco, Colima, and Nayarit—an iconic cultural hallmark. This tradition declined around 600 CE, giving way to localized cultural developments.

Between 900 and 1521, two notable cultures stood out: Aztlán in Sinaloa and Nayarit, and the Purépecha (Tarascans) in Michoacán, who built a powerful state that resisted even the expansionist Mexica.

—Dolores Flores Villatoro, Researcher