During the colonial period, many Otomis learned to read and write their language. Consequently, a significant number of Otomi documents exist from the period, both secular and religious, the most well-known of which are the Codices of Huichapan and Jilotepec. In the late colonial period and after independence, indigenous groups no longer had separate status. At that time, Otomi lost its status as a language of education, ending Classical Otomi period as a literary language. This led to a declining numbers of speakers of indigenous languages, as Indigenous groups throughout Mexico adopted the Spanish language and Mestizo cultural identities. Coupled with a policy of "castellanización" this led to a rapid decline of speakers of all indigenous languages including Otomi, during the early 20th century.