In 1940 Rivera came to San Francisco for what would be his last mural project in the city, Pan-American Unity. Currently housed at City College of San Francisco as a permanent installation, for a time it was in storage and not on public display.During the same period, he created the charcoal sketchentitled Shasta (1940), of large construction machinery that the artist saw near the Mount Shasta dam. He noted the dam and construction equipment as playing a role also in the lives of those living in South Americas.
Diego Rivera was one of the most important artists of the 20th century. He lived and worked for most of his life in Mexico, although he also traveled extensively to such places as Russia, America, France, and Spain. He was (twice) married to the (also extremely famous) Mexican painter Frida Kahlo. Rivera catalyzed the Mexican mural movement in the early part of the century, pushing the national art into a new, socially aware era. He is most famous for his large-scale murals, frescoes, and artistic collaborations that spoke to labor issues, unions, and political radicalism.