Key purchased his first slave in 1800 or 1801 and owned six slaves in 1820. He freed seven slaves in the 1830s, one of whom continued to work for him for wages as his farm's foreman, supervising several slaves. Key also represented several slaves seeking their freedom, as well as several slave-owners seeking return of their runaway slaves. Key was one of the executors of John Randolph of Roanoke's will, which freed his 400 slaves, and Key fought to enforce the will for the next decade and to provide the freed slaves with land to support themselves.