The odds a United States president serving before slavery was abolished owned slaves are 1 in 1.6 (63%). Four of the first five presidents were slave owners.

George Washington acquired his first slaves at age 10. At his death in 1799, 316 slaves were living on his five plantations. Though he expressed sympathy for the “poor wretches” held in slavery, he seemed equally concerned that “this troublesome species of property” would disrupt the fragile union he and other founders had created. In his will, he directed that his personal slaves be freed upon the death of Martha Washington. Tormented by fear that “it was in their interest to get rid of her,” she decided to act while she was still alive, freeing 123 slaves on January 1, 1801.

Thomas Jefferson owed 93 slaves when he was elected president in 1800, and brought about a dozen slaves from Monticello to work at the White House. (Sally Hemings, whose descendants have been linked through DNA testing to Jefferson’s genes, was not among them.) Jefferson lived long enough to foresee that the question of expanding slavery would bring disunion. Hearing of the debate over admitting Missouri as a slave state, he confided to a friend that “like a fire bell in the night,” the situation “awakened and filled me with terror. I considered it the knell of the Union.” He concluded: “We have the wolf by the ears, and we can neither hold him, nor safely let him go. Justice is in one scale, and self-preservation in the other.”

James Madison owned between 30 and 40 slaves, and he too brought slaves with him from his plantation, Montpelier. One of them, Paul Jennings, wrote A Colored Man’s Reminiscences of James Madison, in which he described the president as “one of the best men that ever lived.” Jennings remembered Madison as a man of calm temperament, saying he “never knew him to strike a slave, although he had over one hundred.”

James Monroe, the last of the Virginia Dynasty, had 30 to 40 slaves at the Highland Plantation in Virginia. He had been governor of Virginia during Gabriel’s Rebellion, a slave uprising in 1799, and became convinced that whites could not rely on the “tranquil submission” of blacks. With his friends Thomas Jefferson and James Madison, he endorsed the idea of sending emancipated slaves out of the country. When the American Colonization Society established Liberia for this purpose in 1822, its capital was named Monrovia in honor of the president.

John Adams, wedged in between the Virginians, did not own slaves, though his father-in-law, Reverend William Smith of Massachusetts, owned two. Abigail Smith Adams found the institution morally repugnant. “I wish most sincerely there was not a slave in the province,” she wrote her husband during the Revolution. “It always seemed a most iniquitous scheme to me—(to) fight ourselves for what we are daily robbing and plundering from those who have as good a right to freedom as we have.”

The national capital was carved out of two slave states, Maryland and Virginia. Slavery was legal in the District of Columbia; indeed, there were slave pens on what is now the National Mall. When Abigail Adams arrived at the White House in 1800, then a squalid construction site, she was dismayed to observe the ragged slaves working at the President’s House. “It is true Republicanism that drives the slaves half fed, and destitute of clothing,” she wrote sarcastically, “whilst an owner walks about idle though one slave be all the property he can boast.”

Like Jefferson, John Adams also had a dark sense of foreboding. “I shudder when I think of the calamities which slavery is likely to produce in this country,” John Adams wrote his daughter-in-law in 1820. The Civil War was only four decades away.