On Jun. 26, 1721, smallpox broke out in Boston, threatening to devastate the City. Zabdiel Boylston Adams, a Boston doctor, learned of the smallpox inoculation from Cotton Mather. At the suggestion of Mather, he agreed to inoculate Bostonians. On that same he inoculated his son and two of his slaves against the disease.

Zabdiel also inoculated between 180 and 250 other Bostonians. Many feared that the smallpox inoculations would only spread the disease. They violently opposed Boylston’s work, and his opponents even threatened his family. At one point, one of his opponents threw a hand grenade into his home. Shortly after inoculating his son, Boylston was arrested. Authorities released him after he promised to only inoculate with government permission.

By the early 1800s, most Bostonians understood that inoculation was a valuable tool. But, despite the success of inoculation, smallpox still plagued Boston and other cities. Boston regularly quarantined smallpox patients on Rainsford Island in Boston Harbor. Officials hoped to prevent the spread of the disease to the larger City. Most of the patients on the island were from quarantined ships.