Diego Rivera, Mexico's most revered painter before his 1957 death, also came to be considered one of the most noteworthy artists of the twentieth century. In a visual sense, Rivera's imagery blended Central American folk traditions with European styles, but on a deeper level his works were extensive allegorical portraits of Mexican history, the colonization of the hemisphere, and the development of the modern industrial age. Rivera was able to incorporate such large themes into his work because of the medium with which he is indelibly associated: the wall fresco. After studying the most impressive examples of this method from the Italian Renaissance, Rivera abandoned the small canvas and painted nearly two dozen such extensive murals across North America, some as long as entire city blocks.

Though Rivera is credited with reviving the fresco form in the modern era, at times his art was derided by critics as too...