Houston's Fort was located on Moccassin Creek, in Scott County, VA, near the modern community of Snowflake. It appears as marker 19 on the accompanying map.
Direct information about the construction of Houston's Fort has not been found. Testimony by Mrs. Samuel Scott indicates that in 1776 about thirty people, including ten men, took shelter there during an Indian raid. The size of the party sheltering here would indicate that it was something more than a simple fort house. John Carr, testified that he recalled being held up to a "port hole"  to see the Indians firing on the fort. That implies being inside a building of some description. Overall, it sounds like this was in fact a stockaded fort, perhaps including a blockhouse. [Need specific sources in Drapers MSC for the above]
The land on which Houston's Fort was built was originally settled in 1769 by Thomas McCulloch. McCulloch abandoned the property, in 1771, according to Hamilton, 1968 "because of fear of Indians, though this was two years before the opening of Indian Hostilities in southwest Vrginia. McCulloch assigned the property to Person:William Houston (21) who settled here in 1772. The fort was probably built on this property sometime after the end of Dunmore's War. Eyewitness accounts testify to it being attacked in 1776 a force of Cherokee Indians, said to number as many as 300 men, though this seems to be exaggerated Hamilton tells us that two companies of militia, under Captain Daniel Smith and Captain John Montgomery, came from Fort Blackmore to drive off the attackers.
One well known story associated with this event was the death of Samuel Cowan (?-1776). Cowan lived in Castle's Woods, and road to warn the settlers at Houstons Fort of the impending attack. His wife was Ann Walker daughter of John Walker (1705-c1775) and Ann Houston (c1705-after 1780). Ann is believed to have been the aunt of the Person:William Houston (21) who built Houston's Fort. Her son, John Walker IV (c1735-after 1810) settled adjacent to William Houston's land on Moccassin Creek. Thus Cowan's ride can be seen as an attempt to warn not just settlers, but his own family. Hamilton describes his ride as follows:
Cowan's fatal ride would be the first, but by no means the last, of many KBI and CBI events in the extended Walker family.
The above is largely based on Hamilton, 1968 These are Hamilton's sources. Additional sources and better documentation are needeed: