The transition in Mexico from a maize market once characterized by heavy state intervention along the entire maize–tortilla chain to the ‘free market’ of today has been a long and complex process. Over two decades, the production of maize has seen a radical transition both in the geographical location of maize agriculture and the type of farmers growing maize. In this paper, I argue that the restructuring of the domestic maize supply is due to policy decisions to support private agents in the maize market; hence the state did not withdraw its involvement but, rather, has had a key role in the construction of the ‘free’ maize market, with the result that domestic supply for the market is concentrated in the hands of relatively few agents and in relatively few regions. I discuss the background to these policies and analyse the programmes implemented by the state agency ASERCA (Apoyos y Servicios a la Comercialización Agropecuaria) that support the commercialization of maize.