The idea of inoculating people for smallpox was passed on to Americans by their slaves. If you can fit it, file this under “I Had No Idea.” From Annette Gordon-Reed‘s The Hemingeses of Monticello:
There is no cure for smallpox, and throughout the ages populations across the globe had had to find ways of preventing its spread. Inoculation, also called variolation, after the name of the smallpox virus Variola major, was practiced in Africa, the Middle East, and the Far East. White Americans first became aware of the procedure from African slaves who described it to them. Cotton Mather brought it to the widespread attention of the American public after an African-born slave, Onesimus, told him that he had undergone the procedure while still in his native land and was thus immune to smallpox. In the mid-1700s, after much debate, the American colonies initiated the procedure with great trepidation.
More on Onesimus and Mather here.
IMAGES: Title page, Historical account of the small-pox inoculated in New-England, upon all sorts of persons, whites, blacks, and of all ages and constitutions. London: Printed for S. Chandler, 1726 (James Lind Library); Cotton Mather