There is no doubt that
Benjamin Franklin owned slaves; his newspaper in the 1730s
often featured slaves for sale. Most black servants were slaves, fully owned property
of the master, while many white servants were indentured
George Washington, the first President of the United States, owned over 200 slaves for practically all of his life.
Of the first five presidents, four owned slaves. All four of these owned slaves while they were president.
Of the next five presidents (#6-10), four owned slaves. Only two of them owned slaves while they were president.
Of the next five presidents (#11-15), two owned slaves. Both of these two owned slaves while they were president.
Of the next three presidents (#16-18) two owned slaves. neither of them owned slaves while serving as president.
The last president to own slaves while in office was the twelfth president, Zachary Taylor (1849-1850).
The last president to own slaves at all was the eighteenth president,
Ulysses S. Grant (1869-1877). The Civil War General.........
So twelve of our presidents owned slaves and eight of them owned slaves while serving as president. That would be while the constitution was written without any amendments.