What is the main setting in the novel, Mexico?

Although the primary action of the novel takes place in 1961, there are extended flashbacks to the Indian civilization that existed in Mexico fifteen hundred years before, to Spain in the sixteenth century, to Virginia during the American Civil War in the 1860s, and to Mexico during its revolution in the early twentieth century. The purpose of these flashbacks is to show how the characters present in 1961 have been influenced by history and by their various ancestors.