At the time of the Spanish conquest of central Mexico, Otomi had a much wider distribution than now, with sizeable Otomi speaking areas existing in the modern states of Jalisco and Michoacán. After the conquest, the Otomi people experienced a period of geographical expansion as the Spaniards employed Otomi warriors in their expeditions of conquest into northern Mexico. During and after the Mixtón rebellion, in which Otomi warriors fought for the Spanish, Otomis settled areas in Querétaro (where they founded the city of Querétaro) and Guanajuato which previously had been inhabited by nomadic Chichimecs. Because Spanish colonial historians such as Bernardino de Sahagún used primarily Nahua speakers primarily as sources for their histories of the colony, the Nahuas' negative image of the Otomi people was perpetuated throughout the colonial period. This tendency towards devaluing and stigmatizing the Otomi cultural identity relative to other Indigenous groups gave impetus to the process of language loss and mestizaje, as many Otomies opted to adopt the Spanish language and customs in search of social mobility.