In the process of ‘historizing memory’ the manner by which social actors, events, situations and social processes are constructed in specialized and recontextualized History discourses is crucial. This chapter explores the transmission of official memories of a nation’s recent traumatic past of human rights violations to new generations and its recontextualization in History classroom interactions. In particular, it deals with the valorative reconstruction of Chilean historical memories of Pinochet’s civil-military dictatorship (1973–90) that started with a violent coup d’état that overthrew the socialist government of Salvador Allende in 1973. The study rest on a joint analysis taking into consideration the appraisal system (systemic functional linguistics theory) and the concepts of semantic gravity and semantic density (Legitimation Code Theory) to show how the historical thinking is co-constructed by teachers and students through language interpersonal and ideational instantiations creating cumulative axiological and epistemological knowledge in History classrooms.