The objectives of this study were to analyse the maize diversity in the southeast of Coahuila State in Mexico and to identify a representative subset that encompasses the majority of the diversity in the region of study. Seventy-seven native maize populations were first explored and given a race classification followed by a morphological description based on selected quantitative ear traits using 10 representative ears from the collected samples. The differences between maize populations from the adaptation area and the relationships between and within groups in the region of study indicate the usefulness of the ear traits to describe maize diversity. Two main groups were identified that summarized the maize diversity. The first group, the conical ear complex, includes populations adapted to highland altitudes (Conico Norteño Race). The second group, the cylindrical ear complex, represents populations adapted to lowland and intermediate altitudes (Raton and Tuxpeño Norteño). Using the phenogram, a subset of 18 out of the 77 maize populations (23.4%) was defined that accounts for the variation between and within the different race complexes. This subset also includes at least one representative population from each of the less represented types. The final subset, representing a sample of maize diversity, can be used to establish strategies for conservation and use, such as participatory conservation and management, or it can be used to develop breeding techniques for improving the land race populations within the region of study.