[468] By 1799, slaves at Mount Vernon totaled 317, including 143 children.[469] Washington owned 124 slaves, leased 40, and held 153 for his wife's dower interest.[470] Washington supported many slaves who were too young or too old to work, greatly increasing Mount Vernon's slave population and causing the plantation to operate at a loss.[471]

Abolition and manumission
Main article: Abolitionism in the United States
In 1794, Washington privately told Tobias Lear, his secretary, that he found slavery repugnant.
Based on his letters, diary, documents, accounts from colleagues, employees, friends, and visitors, Washington slowly developed a cautious sympathy toward abolitionism that eventually ended with his will freeing his military/war valet Billy Lee, and then subsequently freeing the rest of his personally-owned slaves outright upon Martha's death.[472] As president, he remained publicly silent on the topic of slavery, believing it was a nationally divisive issue that could destroy the union.[473]
During the American Revolutionary War, Washington began to change his views on slavery.[447] In a 1778 letter to Lund Washington, he made clear his desire "to get quit of Negroes" when discussing the exchange of slaves for the land he wanted to buy.