It is often overlooked that when Robert Weitlaner, Wigberto Jiménez Moreno, and Paul Kirchhoff teamed up with a group of advanced students in a research committee to undertake the survey of the vast territory of present-day Mexico and the adjacent area south to discern and classify the diagnostic traits and boundaries of the area, they submitted a summary report of preliminary results of a work in progress (Jáuregui 2008). The report Mesoamerica (Kirchhoff 1943) was prepared to elicit a thorough analysis and discussion with colleagues in order to enhance a second round of inquiry that was to follow. Kirchhoff expresses in the essay that he is “eager for suggestions concerning the best way to continue this study” (1943: 107, translation by the author), along with a petition for additional research which might have a bearing on the inquiry. The consultation and review Kirchhoff and the committee anticipated never occurred. Mesoamerica as conceived in this brief account was promptly assumed, promoted, and taken for granted (Jáuregui 2008). Half a century later, however, it has begun to receive both the scrutiny and the discussion originally sought by Kirchhoff. Most recently, this stems from the inadequate definition of its northernmost limits where Mesoamerican ideology along the Sierra Madre Occidental has been documented by ethnography (e.g., Jáuregui 2008, 2017; Sociedad Mexicana de Antropología 1990).