Fenn’s attention to detail and use of primary sources is what makes this book so persuasive. Perhaps Fenn’s greatest weakness in her book is the lack of evidence which proves that smallpox actually affected the entire continent. Some regions of the continent such as the Pacific, lack the reports which can fully conclude that smallpox was the disease which left the coastline abandoned and littered with skeletal remains upon George Vancouver’s surprise in 1792. Other plains tribes fall to the same speculation as there are few records which can prove such claims. Fenn, however, is not deceiving. She is very open about this fact, and continually asserts that historians such as herself can only make inferences and logical leaps toward such conclusions. Her honesty is commendable, and adds to her reliability in my opinion. She does argue that makes logical sense that while the cause of death was not recorded in most sources, the mass number of dead during the years 1775-82 would most likely to have been caused by smallpox, especially in the case of the Native Americans as they were the most susceptible to the disease. Much of her primary sources, especially in Mexico and other outlying Spanish colonies derive from libros de entierros, which were the Catholic church’s burial records kept by the friars in the region. These detailed records allowed for Fenn to uncover the mortality rates for the Spanish colonies and track the diseases movement. Aside from the burial records, much of Fenn’s work relies on a mixture of modern biological studies and personal