Henry Brown did not marry Mary "Polly" Ligon. Henry Brown married Susannah Ligon before April 27th of 1805 when she signed away her dower rights to a piece of land that Henry Brown sold, which proves they were married before that date.
Susannah Ligon is a proven daughter of Robert Ligon and Edith Watkins, as Henry Brown was named several times in court documents pertaining to the estate of Robert Ligon. Henry Brown, along with two other heirs, refused to bring forth their advancement to be valued at the request of Edith Watkins Ligon, who was the executrix of Robert Ligon's estate.
As far as I know, there is no proof that Mary was the middle name of Susannah or any document that refers to her by the nickname Polly.
Henry Brown and Susannah relocated to Tennessee by 1820 as their proven son, James Jackson Brown, was born in Tennessee in 1820. They did not leave Spartanburg County, South Carolina until some time after 1813, when another proven son, Henry Washington Brown, was born in 1813. Their kinship is conclusively proven by the wills of Henry Washington Brown and Richmond J. Brown.
My question is why did Henry Brown move to Tennessee and what was he doing during the War of 1812? With Morduca and Aries Brown being so involved in the Revolutionary War, as well as Robert Ligon, I believe it would be unlikely for Henry Brown not to have been involved in some way. However, proof of service has yet to be located for Henry Brown.
If Henry Brown received a land grant for service or if he inherited land granted to either Morduca Brown or Aries Brown, it would explain the relocation to Tennessee and might provide additional documentation on this family.
For the interested, I also have scans of some land records in Henry County, Tennessee. These also include quit claim deeds between Richmond J. Brown and Henry W. Brown to C. W. Foster.