Before the Spanish colonization of the region in 1519, Metztitlán was the site of a powerful, independent Otomi state, unconquered by the Aztec Empire. According to Professor Michael E. Smith, this small kingdom's independence was fortified and maintained as a result of the mountainous terrain in the valley surrounding it. Professor Smith wrote that the factors behind the state's enduring independence was due to the fact that "there were few resources of interest to the (Aztec) Empire in this area, and the final emperors may have decided that Metztitlán was not worth the effort."