By the 16th century smallpox was well established all over Europe. Because of European exploration and colonization the disease was spread to other parts of the world. Smallpox devastated the native Indian population in the Americas and 400,000 Europeans died each year from smallpox epidemics. In America Boston, Massachusetts was plagued by a smallpox outbreak in 1690 and 1702. In 1706 Onesimus, a slave, advised his master Cotton Mather, a Puritan clergyman that in his homeland of Africa he had undergone an Operation to combat smallpox. The centuries-old practice, Inoculation was practiced throughout Africa and involved the extraction of material from the skin of an infected person and, using a thorn, scratching it into the skin of the unaffected person. The introduction of smallpox gives the inoculated person immunity from the disease. Cotton Mather in a 1716 letter to the Royal Society of London proposed a “ye Method of Inoculation” as the best means of curing smallpox and noted that he had learned of this process from “my negro-man Onesimus, who is a pretty intelligent fellow”. Most white doctors rejected this process of deliberately infecting a person with smallpox because of their misgivings about African medical knowledge. Public and medical opinion in Boston was strongly against both Mather and Dr. Zabdiel Boylston, the only doctor in town willing to perform this inoculation. A survey of the nearly 6,000 people who contracted smallpox between 1721 and 1723 found that Onesimus had been right. Only 2 percent of the 600 Bostonians inoculated against smallpox died. Bostonians and other Americans would soon adopt the African practice of inoculation in future smallpox outbreaks and this would remain the most effective means of treating the disease until the development of vaccination by Edward Jenner in 1796. Onesimus’ recollection of a traditional African medical practice saved numerous lives and sparked the introduction of smallpox inoculation in the United States.