Based on the limited official records that have survived, it appears that Colonel Thomas Fletchall was originally a native of Maryland, the son of Thomas (known as "Poor Thomas" by Fletchall family genealogists) and Elizabeth Fletchall. Colonel Fletchall was born in about the year 1725 as his memorial, dated 16 July 1787, states that he was then "upwards of 62 years old." In about 1755, Fletchall and his family removed from Frederick County, Maryland and settled in the backcountry of South Carolina. By the 1770s, the site of Fletchall's main plantation was in the Fairforest Creek region of South Carolina; he was a justice of the peace, a coroner, and a colonel of militia for the Ninety-Six District.

In 1773, Fletchall and one of his constables, John Mayfield, were sued in the Charles Town Court of Common Pleas by a certain John Nuckolls. The lawsuit basically concerned John Mayfield's arrest of Nuckolls, John being a constable operating under the orders of the local magistrate (justice of the peace), Thomas Fletchall. Nuckolls's argument was that he had been apprehended in NC, where a warrant issued by a SC magistrate had no legal standing.

It would appear that Nuckolls was apprehended in that part of SC which SC historians refer to as the "New Acquisition Territory." This area had previously been considered part of NC; however, in 1772, the dividing line between NC and SC was finally surveyed as far as the Cherokee Indian Line. The result was that much land previously thought to have been in NC was found to be actually in SC. In fact, the 300-acre tract acquired by John Mayfield from Jacob Brown in 1770 was also in this area, as Brown had obtained title to the land by patent issued by the Province of North Carolina in 1754.

It is interesting to note that Fletchall and Mayfield were represented in court by Edward Rutledge (1749-1800). Edward was the younger brother of the more famous John Rutledge (1739-1800). In 1776, Edward would be the youngest man to sign the Declaration of Independence. Subsequently, on 12 May 1780, Edward, then a Lieutenant Colonel in the Whig forces, was taken prisoner by the British when Charleston was captured by troops under the command of Sir Henry Clinton. Rutledge remained a British prisoner until exchanged in July 1781.

In 1775, Thomas Fletchall was considered by the Whig "Rice Kings" of the Charleston area to be one of the most influential men in the South Carolina backcountry. Although not a particularly brave man, Fletchall was loyal to the king throughout the Whig-Tory conflicts of 1775. Even though he could have acquiesced and embraced the Whig Cause without any loss of personal position or wealth, he steadfastly refused to take up arms against his king. For his loyalty, he was imprisoned at Charleston from December 1775 to July 1776 and lost all of his official public offices.

He was pleased when Charleston was captured by the British in May 1780, but took no active part in the conflict with the Whigs in South Carolina. His most serious acts taken during the British occupation of South Carolina seemed to involve entertaining and providing dinner for various British and Loyalist officers at his Fairforest plantation. Even though he had committed no overt acts against the Whigs, after the Battle of Kings Mountain in October 1780, death threats from his Whig neighbors caused Fletchall and his family to flee to British occupied Charleston. In December 1782, he was evacuated, along with many other Loyalist refugees, to the British controlled Island of Jamaica. Thomas Fletchall remained in Jamaica until his death in the year 1789. All of his South Carolina estates were confiscated.