According to Wikipedia:
The earliest-known telling of the tree’s story comes from a front-page article entitled "Deeded to Itself" in the Athens Weekly Banner of August 12, 1890. The article explains that the tree had been located on the property of Colonel William Henry Jackson (no relation to the photographer). William Jackson was the son of one James Jackson (a soldier in the American Revolution as well as a Congressman, U.S. Senator, and Governor of Georgia), and the father of another James Jackson (a Congressman and Chief Justice of the Supreme Court of Georgia). He was the brother of Jabez Young Jackson, also a Congressman. (William Jackson was reportedly a professor at the University of Georgia, and is sometimes given the title of Doctor. The nature of his military service and the source of the title "Colonel" are unknown.) Jackson supposedly cherished childhood memories of the tree, and, desiring to protect it, deeded to it the ownership of itself and its surrounding land. By various accounts, this transaction took place between 1820 and 1832. According to the newspaper article, the deed read:
I, W. H. Jackson, of the county of Clarke, of the one part, and the oak tree… of the county of Clarke, of the other part: Witnesseth, That the said W. H. Jackson for and in consideration of the great affection which he bears said tree, and his great desire to see it protected has conveyed, and by these presents do convey unto the said oak tree entire possession of itself and of all land within eight feet of it on all sides.
I couldn't help noticing this bitter fact - if the transaction granting the Tree ownership of itself happened between 1820 and 1832 it means that for around thirty or forty years there was a tree in Athens Georgia that owned itself, while millions of human beings in that state and adjoining states did not own themselves.
Other famous trees.