For the past year I have been living in Richmond County to do research on my ancestors who lived here in the mid-1600s to the mid-1700s.I have a booklet "Historical Atlas of Westmoreland County, Virginia" by David Eaton:
"page 39 - Christopher Morthershead bought land from William Lord on a branch of Pope's Creek, 150 acres, and he was probably the emigrant of the large family of that name."
There was no date given, but a John Lord owned land where Montross is now located in 1667.It is mentioned on another page that he had one son named William who owned land on Pope's Creek; again,no date.
"Page 41 - Humphrey Quisenbury, son of John Quisenbury and Ann Pope, was born about 1670 In Westmoreland County, Virginia, and died in King George County, Virginia, in 1727, married Elizabeth Mothershead, a daughter of John Mothershead of Westmoreland County.His son Humphrey, had a daughter, Mary, who married John Marshall,uncle of Chief Justice John Marshall."
I did not see any other listings for the name Mothershead in the index of this booklet.