A group of related Cowans, often assumed to be brothers, settled in Southwest Virginia about 1772. These included:
Samuel, Andrew and William married Ann, Mary, and Jane Walker, daughters of person:John Walker (85) and Ann Houston. Based on their marriage to sisters Samuel, Andrew, and William are believed to be brothers, though direct evidence for this is limited. David is possibly a brother brother as well, but direct supporting evidence for this has not been developed.
David Cowan settled in Castle's Woods by 1769, on what is today known as Mill Creek, near the modern community of Castleswoods. During Dunmore's War a small, possibly palisaded fort, was established on his property for defense against the Indians. Following the revolution David removed to Sevier County TN, where he lived out his life.
Samuel Cowan settled a bit further to the west, near Moore's Fort in colonial Castle's Woods. Samuel is not shown to be in the area until 1772. He was killed by Indians about 1776, in a well known and amply documented event. His wife Ann Walker was captured by Indians the following year. His son person:John Cowan (12) inherited his fathers property; county records indicate that he left the area about 1786, eventually settling with kin in the Blount County area, in the Little Tennessee watershed, not far distant from his uncle David.
William does not appear in the records of the area until 1776. Like Samuel, it is possible that he came to the area early on, living perhaps with their brother David. It is also possible that he did not arrive in the area until considerably later than David, possibly in response to the death of Samuel in 1776. William settled in the original Castle's Woods community west of Mill Creek, near Moore's Fort. Following the revolution he removed to Blount County, settling on the Little River, near his brotherinlaw, John Walker IV.
Andrew also appears in the records of the area for the first time in 1776.I t is not exactly clear where he settled; land records indicate that he owned land near the Rye Cove area, on the North Fork of the Clinch, but it is not clear that he lived there. His son, Andrew Jr. eventually settled near Cedar Creek, north of Castle's Woods, and his father may have lived in this area. Andrew Cowan was a prominent figure in the community, serving as a captain in the militia, and eventually being designated "Gentleman", serving among the first Justices of the newly formed Russell County. [veryify county] It is believed by many that Andrew moved to Jeffeson County, Tennessee about 1793, well after his brothers left the area. There is, in fact, an Andrew County who appears in Jefferson County after that date, but it is not clear that he is the same person who served as a Justice in southwest Virginia. Certainly Andrews son, Andrew Jr. remained in southwest Virginia for the remainder of his life.
There is limited evidence for the presence of other Cowan's in the Holston River Valley to the east of Place:Castle's Woods, but this has not been explored.
The primary issue for the Cowan's of Southwest Virginia is determining where they came from, and identifying their parents. There is a common view that they came from the Borden's and Beverly's Grant area of Virginia (modern Rockbridge and Augusta Counties). There were in fact Cowan's living in those area's. The fact that John Walker III, and Ann Houston, parents of the wives of three of the Cowan brothers, were from that same general area also suggests that the Cowan's came to Southwest Virginia from that area. However, direct evidence of this is lacking, and the similarity of names may be simply coincidence. 
The surname is sometimes rendered as "Cowen", though the "Cowan" spelling predominates in southwest Virignia and elsewhere. "Cowin" is a rare variant. It is possible that some common surnames, such as "McCown", are variants of "Cowan", though this does not seem likely. "Cohen" may have been anglicized to "Cowan" in some cases.