From NKAA, Notable Kentucky African Americans Database (main entry)
Clark, John Milton and Lewis George (brothers)
The Clark brothers, John Milton (1820-1902) and Lewis George (1818-1897), were born in Madison County, KY. Their father was a white weaver from Scotland. Their mother, Letitia Campbell, was the daughter of plantation owner Samuel Campbell.
John and Lewis were at times seen as white slaves. The brothers escaped in 1842, Lewis to Dawn, Ontario (he later went to Oberlin, OH), and John to Cambridge, Massachusetts, where he became the first African American elected to a public office on the Cambridge Common (City) Council. The character George Harris in Uncle Tom's Cabin was based on Lewis G. Clark.
For more see Narrative of the sufferings of Lewis and Milton Clarke, by L. G. Clark and M. Clark [full-text at the website by S. Railton & the University of Virginia];"J. Milton Clarke 1820 - 1902 and Lewis Clarke 1818 -1897: Writers and Abolitionists," in the Cambridge African American History Marker Database; Funeral of John Milton Clarke at The Cambridge Chronicle website; and Literature in The Economist, 2/13/1847, p. 183.