This dissertation analyzes the social-spatial knowledge practices that have emerged in the controversy over genetically modified (GM) transgenic corn in Mexico. This controversy is embedded within a broader struggle over the future of global food production and consumption, as the idea of agrobiotechnology as a techno-fix to global climate change and hunger increasingly takes over the popular imagination. The concept of food sovereignty, as developed within the Vía Campesina social movement, has emerged as a powerful discursive alternative on this terrain. Mexico is one of the most active sites of dispute over the future and meaning of maize and small-scale farming in North America. Through ethnographic and discursive engagement with the key social movement network that has emerged "in defense of maize" in Mexico, this dissertation analyzes the practices that have worked to generate autonomy and alternative geographies of territory and justice in the struggle over transgenic maize between the years 2009 and 2014. The complexity of intertwined cultural and biological processes that give rise to agrobiodiversity make studying the cultural politics of maize and the rearticulation of agrarian progress particularly relevant in maize's "center of origin." This project describes and analyzes three specific, concrete sets of world-making practices taking place at different sites of struggle against transgenic corn in Mexico: testing, mapping, and the international Permanent People's Tribunal. These practices emerged in moments of crisis--of contamination, of defining the centers of origin of maize, and of state impunity--framed within the larger discourse of crisis that sees rural Mexico as under "attack" by the Mexican government, starting with the neoliberal reforms of the 1980s. Each site of struggle has changed the terms of resistance through experimentation, specifically generating practices of autonomy and multiplicity.