This paper explores the intersection of race science and plant taxonomy in the creation of evolutionary taxonomies (phylogenies) of populations of Zea mays, also known as maize or corn. Following recent work in the history and sociology of race, it analyzes maize taxonomy as technology. Through an analysis of successive attempts to classify diverse maize varieties, especially those originating in Mexico, it shows that taxonomy created possibilities for researchers to intervene in commercial agriculture, state development projects, biological conservation, and domestic and international politics and policy. It further underscores that the modern science of maize taxonomy was distinct but never inseparable from assessments of maize's human cultivators. Attending to particularities of this relationship is crucial, because it reveals the application of maize taxonomy as a technology for ordering human diversity, and intervening in human lives, as well as managing the impressive diversity of Zea mays.