I have a copy of Cecil C cammack's book and it contains a lot of detail on your family. McKinney Cammack is mentioned and the tree goes back to the William and Lieutency Cammack. This William Cammack, Cecil says was the son of John Cammack and Mary Parker and grandson of John cammack and Margaret Purtle of Laurens County.
There is lots of infromtaion on this family on the web, see http://www.growintree.com/surnames/cammack.html