Chicano muralism, which began in the 1960s, became a state-sanctioned artform in the 1970s as an attempt by outsiders to "prevent gang violence and dissuade graffiti practices." This led to the creation of murals at Estrada Courts and other sites throughout Chicano/a communities. In some instances, these murals were covered with the "placas" they were instituted by the state to prevent. Marcos Sanchez-Tranquilino states that "rather than vandalism, the tagging of one's own murals points toward a complex sense of wall ownership and a social tension created by the uncomfortable yet approving attentions of official cultural authority." This created a division between established Chicano/a artists who celebrated inclusion and acceptance by the dominant culture and younger Chicano artists who "saw greater power in renegade muralism and "barrio" calligraphy than in state-sanctioned pieces." Chicano poster art became prominent in the 1970s as a way to challenge political authority, with pieces such as Rupert García's "Save Our Sister" (1972), depicting Angela Davis, and Yolanda M. López's "Who's the Illegal Alien, Pilgrim?" (1978) addressing settler colonialism.