1.  See Mary Clarke's  Genealogy of the Clark Family.  There is more information there.

2.  LDS.  Family Search: Internet Genealogy Service: Ancestral File.

I'm concerned about the link from Joanna CLARK to this Watson CLARK.  The family group sheets at Mary Clarke's web site are well documented, and they show Watson CLARK as b. ca. 1750 in New Jersey, while the LDS Ancestral File has him born ca. 1759 in Montgomery Co., MD.  There seems little doubt that Watson was born in New Jersey because although Abraham later moved to Virginia, he was known to be in New Jersey at least as late at 1759.  If Joanna's father truly was born in Maryland in 1759, then he cannot be the son of Abraham CLARK.  Nor is it likely that Watson's children would have been born in Maryland.  Historical records do show that the Watson CLARK who married Sarah SCOTT was the son of Abraham CLARK.  If so, what is messed up here is the birthplaces and birthdates in the LDS Ancestral File.  However, historical records giving Watson's children do not include a "Joanna."  Also, the AF shows Sarah BADGLEY as the mother of Watson, but she was the second wife of Abraham and not the mother of Watson — the identity of Watson's mother is unknown.  On the other hand, again, a son of Isaac's (son of Watson) married a NIXON, as did Joanna.  There is much work to be done to confirm this link.