I did find Elizabeth Dawson in the 1850 Census for Nelson County, Virginia (not Upshur) in the household of Ira Foster, the son of Thomas Foster and Helena Humphrey of Albemarle (and later Louisa), and the brother of my ggg grandfather, Thomas F. Foster. Ira and Thomas were blacksmiths, as was their father.
Unfortunately, she is listed as having been born in Virginia, as is Stephen, who is listed as such throughout the remainder of his life -- naming Albemarle as his county of origin. I have read the History of Upshur County pertaining to the Dawsons and find it odd that Stephen would list Albemarle as his place of birth if he had been born before 1812 when Hiram allegedly emigrated from Scotland to Virginia. I HAVE found a Hiram Dawson that lived in Orange County, Virginia, in the 1820 Census with a family that fits the ages necessary and find him again in 1830 Census but this time in Albemarle County.
I will be glad to examine the Personal Property Tax lists in Orange, Albemarle, and Nelson counties to see when they moved and when Hiram may have died. I am positive that the Hiram listed in Albemarle in 1830 is our guy. He was born in the late 1760s or early 1770s.
I also notice that there is a Chancery Court record in Nelson County from 1842 concerning Elizabeth Dawson brought by a John Bailey. I will be happy to read through this, too. If the names on link below have any meaning, surely it is that this is the right Elizabeth Dawson and it will make mention of her family:http://www.lva.virginia.gov/chancery/case_detail.asp?CFN=125...
While it is possible that there was a Hiram Dawson in Scotland that came to Virginia and died shortly thereafter, as it states in The History of Upshur County, I see no record of it in immigration sources.
I am willing to bet that I can find record of Hiram Dawson's will in Albemarle or Nelson and certainly can find record of Elizabeth's death. Since she was already being sued in 1842 by someone and the case lists a lot of names, I bet she was being sued as an heir of her late husband, Hiram.
My bet is they are not from Scotland, at least as immediate as an 1812-1814 immigration, since Stephen was born before that time and lists his origin as Virginia, and because his mother, Elizabeth Dawson, lists her origin as Virginia. This is not foolproof but tends to strongly suggest that they were already established in Virginia.