Analysis of 1780s Head right Land Grants, Hardin and related, from the records I've found so far.
by Travis Hardin, 5 Dec 2014

ISAAC HARDIN
Isaac Hardee received a governor's grant on 1 Dec 1786 of 600 acres on Williamson Swamp in Washington County. "The act of Feb 22, 1785  delegated to the land courts of the ten counties in the state the duty of issuing warrants, without the necessity for a governor's certificate. The act provided that no bounty grants would be allowed after Feb 22, 1786; however a warrant issued by the latter date would not become out of date if surveyed within two years of that date." -Hitz, 1954. The acts that required a governor's grant were those of Feb 17, 1783 and Feb 25, 1784. The latter opened Washington and Franklin Counties. It also required living on the land one year and cultivating 3% of it. Therefor if the law was followed (very often not the case), Isaac "Hardee" arrived and ordered a survey before Dec 1, 1785. On Feb. 24, 1785 Isaac Hardin was appointed road overseer in northern Moore County "from the Chatham County line." His travel time and arrival date in Washington County, Georgia was between those two dates (Feb 24 to Dec 1, 1785).

Isaac Hardee was granted 600 acres in Washington County on Williamson Swamp, implying seven children if there were two parents. The mother would have been Rachel, age 16 (b. 1769). The children based on census data would have been MALE 1 b. bef 1774, FEMALE 1 b. bef 1774, FEMALE 2, MALE 2 b. 1775-90, MALE 1 & 2 OF SECOND WIFE b. 1785-90, and an unidentified, probably older child of the first wife, making seven. The second wife Rachel was no more than 16 when the family traveled and two boys were infants. Alternately, the first wife traveled to Georgia in 1785 with two other, grown, children instead of the two boys b. 1785-90 who were (alternately, I say) born to Rachel nearer to 1790. Alternate 2, MALE 3 born 1791-1800 was the first child of Rachel, one born in Union or Pendleton District, South Carolina.

Consult my "Isaac Hardin Deductions as to Ages of Children" for working out ages from the census.

From a psychological point of view, I believe a great upheaval including loss of his farm and loss of his wife would more likely encourage a totally new location with a new wife than would only the news of free land in Georgia. I would stay with my first impression, though it means a 34 year-old or older man married a 14 or 15-year-old girl. It is by no means that unusual in the days of yore. My own grandfather Hardin married a 15-year-old in 1915.    

1787: Isaac "Hardy" is in the Georgia Colonial and Head right Plat Index for 148 acres in Wilkes County. On March 11, 1789 Isaac Hardy was called into Wilkes Superior Court to answer a charge by John Lindsay that on or about Feb. 20, 1789 he took 3000 weight of tobacco worth three hundred pounds specie. Any sheriff was authorized to bring him in for trial. It appears Isaac "Hardy" lived on his claim near his neighbor John Lindsay. By census day in August 1790 Isaac Hardin lived in Union District, SC among some former Chatham County neighbors. I believe Isaac Hardin, to avoid going to trial, removed himself and his family from Wilkes County and from Georgia in March 1789.

How Isaac Hardin abandoned his Washington County property and took up in Wilkes County I do not know. Reference 2, Hitz 1954, tells us no law prevented the holders of warrants or certificates from selling them to others, who would present the warrants to lands courts who would issue new warrants in the purchaser's name.

Isaac Harden (with that spelling) is mentioned as having applied for 200 acres in Wilkes County which was subsumed in a larger claim by John Holden on 6 Sep 1789. I believe the "old warrant of Isaac Hardin's" claimed in September by Holden was the 148 acres on which Hardin lived when he left the state in March.

ADAM HARDIN    
 
1788: Adam "Hardy" is in the Georgia Colonial and Head right Plat Index for 290 acres in Washington County on Sandhill Creek. The Feb. 22, 1785 statute was in effect: No purchase price, only fees; and cultivation was no longer required. No surveys were to be made after Feb. 22, 1786. His descendants write about Sandhill Creek, so Adam received title by some means. The number of acres, 290, is probably explained under the provisions of the Act of Feb 25, 1784 under which bounty grants (for soldiers) were issued in Washington County with a 15% increase in previous acreage instead of being tax free for 10 years. The following were to receive 287.5 acres: Privates in Minute Battalions; Privates in Militia; Refugee Private in Militia; Seamen in Galleys; Citizens; and Deserter from British. The amount of land received by Adam "Hardy" implies he was in one of the above categories. It says nothing of his marital status.

Adam's Washington County survey was two years after his cousin Isaac's. 

On 1789 Oct 29, Adam Harden (with that spelling) received 200 acres in Wilkes County "by Wheeler's lands." The deed was registered on 10 Nov 1789. Note this date is after the theorized departure of Isaac Hardin from Wilkes County.

1790 June 14 Adam Harden receives title from Governor Telfair for 290 acres in Washington County. It was registered 2 days later. The land adjoined Anderson, Braswell, Burk, Wood and Williams.  

DAVID CLAY (who married Eve Hardin)

1785 Dec 5 David Clay receives a warrant of survey for 200 acres in Washington County on Buffalo Creek. It may be a coincidence that Isaac Hardin warrant was in the same month. David Clay's, dated Dec 5, 1785 was in Book F p. 350; Isaac Hardin's, dated 1785 was on page 365.

I am unclear which brother EVE HARDIN traveled with and when, or when and where she met David Clay. Did they travel together from Chatham County or meet in Georgia? She married him Sep 26, 1792 in Warren County, at least seven years after he appears in Georgia.