I'm a descendant of John Cowen of Smithfield, Rhode Island, who married Sarah Mitchell in 1718 at Providence, RI.
My roadblock is figuring out where he came from. Is he a descendant or relative of SPOW John Coehon of the John and Mary, known as John Cowen of Scituate, MA, a Scottish prisoner who married Rebecca Short (widow of Richard Mann) in at Scituate in 1656?
The likeliest solution is in a Y-DNA test of the right person. 
If you are descended from one of the sons of John Cowen/Cowing of Scituate (John or Israel) please take a test and join the Cowan/Cowen/Cowing surname project. I have lots of info on this family if anyone is interested ...