After the Mexican Revolution of 1910–20, the education minister José Vasconcelos launched an unusual programme to rebuild national identity: the walls of ministries, schools and palaces were allocated to artists. The reasoning was practical — much of the population could not read, and a mural reached where a book could not.

Three figures stood out. Diego Rivera combined Italian fresco technique with pre-Columbian visual language to build a historical narrative of conquest, exploitation, revolution and labour. José Clemente Orozco was darker, painting the violence of the revolution and the way ideologies crush people. David Alfaro Siqueiros worked on technique — spray gun, synthetic paint, perspective on angled surfaces — and designed his walls for a viewer in motion.

Rivera's Detroit Industry, made for the Detroit Institute of Arts in 1932–33, is the programme's largest example outside Mexico: he spent weeks observing Ford's River Rouge plant and painted the assembly line, the workers and the machine at the scale of a creation narrative. The mural he made the same year for Rockefeller Center was chiselled off before completion because of a portrait of Lenin in it — the question of whose money carries whose message in public art took concrete form in that episode. Muralism directly influenced the federal mural programmes of the Depression in the United States; Pollock encountered pouring technique in Siqueiros's workshop. The idea that art can be public and political work outside museum and gallery runs on to the street art of the following century.