There does not appear to be a consensus on the number of men who signed the U.S. Constitution—or, more broadly, were delegates to the Constitutional Convention of 1787—and who were also enslavers.
According to the Gilder Lehrman Institute for American History, “about 25” delegates enslaved people, of the 55 who attended the convention’s proceedings in Philadelphia. The Constitutional Rights Foundation asserts that 17 of the 55 delegates were enslavers and together held about 1,400 enslaved people. In addition to identifying James Madison as an enslaver, Signers of the Constitution, published in 1976 by the National Park Service, notes that 11 other signers “owned or managed slave-operated plantations or large farms,” and then it names them: Richard Bassett, John Blair, William Blount, Pierce Butler, Daniel Carroll, Daniel of St. Thomas Jenifer, Charles Pinckney, Charles Cotesworth Pinckney, John Rutledge, Richard Dobbs Spaight, and George Washington. It is also known that Benjamin Franklin enslaved people.