Chicana/o film is rooted in economic, social, and political oppression and has therefore been marginalized since its inception. Scholar Charles Ramírez Berg has suggested that Chicana/o cinema has progressed through three fundamental stages since its establishment in the 1960s. The first wave occurred from 1969 to 1976 and was characterized by the creation of radical documentaries which chronicled "the cinematic expression of a cultural nationalist movement, it was politically contestational and formally oppositional." Some films of this era include El Teatro Campesino's "Yo Soy Joaquín" (1969) and Luis Valdez's "El Corrido" (1976). These films were focused on documenting the systematic oppression of Chicanas/os in the United States.