Source:Chalkley's Chronicles provides entries for 14 given names associated with the surname "Cowan/Cowen" in Old Augusta.  The earliest entries date to 1746, indicating that the Cowan's were probably not among the very earliest settlers (who date to about 1738), but either came to the area somewhat later, or if at an early "first wave" date, left no records to tell the tale.
James, Andrew Cowan, and John Cowan were the earliest Cowan's for whom we have surviving records, and settled on Beverley's Manor. It seems likely that they are closely related, but their exact relationship has not been established. Birth records suggest that they were assoicated with the Tinkling Springs Presbyterian Church. Many believe they came to Old Augusta from Old Chester. If so, they may be related to the Presbyterian Pequea Creek Cowans of Lancaster County, though other affinities can not be rules out. Source:Fleming, 1971 equates these Cowans with Seven Cowan Brothers, but the available data does not support his conclusions. YDNA test results seem to confirm this affinity, for most, though not all, early Cowan's in the area
After 1750 other Cowans appear in the record. Most are probably children or kindred of the earliest Cowan arrivals, but some, such as Person:Joseph Cowan (4), are likely to be unrelated to the earliest Cowans in the area. In anycase, evidence suggests that many of the early Cowan's in Old Augusta, left the area 1760's, moving south toward the Carolinas, or perhaps into Southwest Virginia. (See Analysis. Dispersion of Old Augusta Cowans). While the Cowan surname appears with some frequency in the records after the 1760, most of those records either explicitly show that they have left the area, or can be interpreted that way. While some Cowan's do remain in the area, their relation to the earliest Cowans is unclear.