How Onesimus, a Slave in Colonial Boston, Helped Stop a Smallpox Epidemic

Considering that, by the mid-19th century, slave labor and the slave trade itself were powerful economic engines in the American South, it's surprising that, 200 years before, Massachusetts was actually the first colony to give human slavery the moral and legal thumbs up, codifying the right to own human chattel in 1641. By the time Onesimus was purchased for the famous Puritan minister Cotton Mather in 1706, there were about 1,000 enslaved people living in Massachusetts — about a third of them living in Boston. Some of these people were indentured servants, and not all were of African descent — some were from Europe and some were indigenous native Americans. However, the turn of the 18th century saw the colonies putting more restrictions on people of color, and disproportionately binding them to slavery for life.

Nobody knows Onesimus's original name — Cotton Mather named him for a biblical slave who escaped his master, but who later converted to Christianity. He was probably born in West Africa and brought to the colonies on a ship in his youth, as Mather described him as "a young Man who is a Negro of a promising aspect of temper" in his diary the week his congregation presented Onesimus to him as a gift.

Cotton Mather was an important Bostonian — his father, Increase Mather, was the president of Harvard, a job that Cotton Mather later turned down because what he really wanted to do with his time was read and write. Mather was considered among the most educated people in the colonies, and he published upward of 400 books in his lifetime, on everything from piracy to plant hybridization. Mather was also a religious zealot — in the 1690s, he figured prominently in the Salem witch trials, earning himself the reputation of being extremely anti-witch.

Because Mather lived in the city and spent most of his time reading and writing, he was ostensibly not much in need of a laborer in his home — Onesimus's main jobs in the Mather household seem to have been clearing snow, stacking firewood, carrying water and doing little chores around the house. However, Mather was extremely interested in converting Onesimus to Christianity, and he wrote in his diary about teaching his slave to read and write so that he could better understand the Christian catechism.

Perhaps because Mather was so adamant about converting Onesimus to Christianity, the two seem to have chatted a lot.

"It was a relationship between an owner and someone who was owned, but we know a lot more about Onesimus than we do about other African Americans of the time because Cotton Mather's diary is very detailed," says Steven Niven, executive editor of the African American National Biography at Harvard's Hutchins Center for African and African American Research. "We know, for instance that he had a son who died. We know, too, that Onesimus wanted to buy his freedom from Mather, which we can assume he eventually did."

Mather's diary also details how sometime in the early 1700s, he and Onesimus had a conversation about the extremely deadly smallpox epidemics that swept through New England in the 40 years prior. At the time, smallpox was one of the deadliest diseases in the North American colonies, and Boston had been hit hard several times. According to Mather's diary, during one of these conversations, Onesimus made a remark that he wouldn't be getting smallpox if it came back through Boston because he had been inoculated before he left Africa. Of course he didn't use the term "inoculation," but he explained to Mather that he had,

The process Onesimus underwent back in Africa is now known as variolation, which was the deliberate infection with the disease in order to create immunity from it, and he explained to Mather that you could tell from the scar on someone's arm that they had been treated. Even people who are selling or purchasing slaves knew to look for the scar because that person was more likely to survive a smallpox epidemic, and therefore more valuable.

Mather didn't act immediately on this information, but in 1720, when Boston experienced another smallpox outbreak, he remembered the conversations he had had with Onesimus. Mather teamed up with a physician named Zabdiel Boylston and campaigned to inoculate the people of Boston against the disease in the same way Onesimus had been inoculated back in Africa.

"Although Cotton Mather was a very important figure in Boston at the time, and people listened to him, most of the community was opposed to this idea for a couple of reasons," says Niven. "One is because this was a practice the Africans used — it wasn't used in Western Europe at the time, and people were very wary of that. Secondly, there was a newspaper in Boston called "The New England Courant" run by Benjamin Franklin's older brother, James. It mounted a slander campaign against Cotton Mather, saying it was ridiculous to think you could protect somebody from a disease by giving them the disease."

In the end, 242 people volunteered for Mather's inoculation crusade, and only 2 percent of those people died in that smallpox epidemic, compared to 14 percent of the uninoculated population who died of smallpox in Boston between 1721 and 1723. When the word spread that those who were inoculated had a seven times greater chance of surviving smallpox, it became a common practice in Boston and the rest of the Americas until 1796 when Edward Jenner developed the first smallpox vaccination.

What Onesimus thought of the part he played in saving the lives of countless colonists is unknown because, according to Mather's diary and other documentation, he succeeded in conditionally buying his freedom around 1716. He bought Mather a replacement slave, and agreed to do small jobs around the house, when necessary.

As far as anyone knows, though, Mather never succeeded in converting Onesimus to Christianity.