John Witherspoon's place in American Presbyterianism

A great number of important 18th and 19th century American Presbyterian theologians could find John Witherspoon as their personal teacher or as a teacher of their teacher to a higher degree. There are important exceptions to this chart. For example, James Henley Thornwell and Robert Lewis Dabney (two important Southern Presbyterian theologians) did not have teachers in this lineage.
I had first made this chart to see the importance of Archibald Alexander, but it seems John Witherspoon is even more central.