Diego Rivera in Detroit

During the 1930s Diego Rivera was considered the world's greatest muralist. Influenced by the Mexican Revolution, his art used the public mural form to emphasize the perspective of the common person, especially the Mexican laborer, peasant and Native American. Rivera was interested in the history of the conquest of the New World, in the ongoing exploitation of working people. Rivera forged a distinctive style fashioned from a unique fusion of indigenous pre-Columbian art, European Modernism, particularly Cubism, and early Italian Renaissance fresco painting. (Mario Pereira)
In the Detroit Art Museum Rivera created a mural that became controversial. From an article on the NPR website:

In 1932 Edsel Ford, the son of Henry Ford and president of the car company that bears the family name, and William Valentiner, the director of the Detroit Institute of Arts, commissioned Rivera to paint two murals for the museum's Garden Court. The only rule was the work must relate to the history of Detroit and the development of industry.

Soon thereafter Rivera and his wife, painter Frida Kahlo, arrived in Detroit and began studying and photographing the Ford automotive plant on the Rouge River. The factory so fascinated and inspired Rivera that he soon suggested painting all four walls of the Garden Court. Ford and Valentier agreed and soon Rivera's commission was expanded.