It is fairly well known that in 1890 Guillermo Prieto was crowned the most popular poet in Mexico. Students of Mexican literature will add that he also wrote articles on manners and customs, criticism, original dramas, satire, travel books and folklore. Those who delve into political science have discovered that he served in the national congress for some forty-eight years, that as postmaster general he reorganized the Mexican postal system, and that he served four terms as minister of finance. Some have even seen the fat tomes in which he published his views on political economy, but practically nobody today knows that Prieto was also a writer of history. The purpose of this paper is to shed more light on Guillermo Prieto as a historian.