October 22, 1757 - February 7, 1814
William was probably also educated by tutors at Gunston Hall. During the Revolutionary War he had been a member of the Fairfax Militia fighting under "Light Horse" Harry Lee in South Carolina; he was commissioned a Captain. In a 13 December 1780 letter, George Mason refused an offer by Lee to continue his son’s military service:
I have received your favor of the 30th November, and have the warmest sense of your very friendly offer to my son William, whose inclination I well know would strongly incline him to accept it, in which I would most cheerfully indulge him if I had any thought of continuing him in the military line...But I have ever intended him for civil and private life; his lot must be that of a farmer and gentleman…
William returned to private life between December, 1780 and June, 1781. In 1780, at age 23, he inherited Mattawoman, the Eilbeck estate in Charles County, Maryland, from his grandmother, Sarah Eilbeck. He also received all his father's lands in Charles County, Maryland. However, it is very likely that William Mason continued to reside at Gunston Hall until his father’s death.
The year after his father died William married Ann Stuart, the daughter of William and Sarah Stuart of King George County, Virginia. William Stuart, ordained in London after studying theology there, eventually succeeded his father as rector of St. Paul's Parish in King George County. As Mason family records show, William Stuart presided at many Mason family celebrations and ceremonies.
Ann Stuart, July 11, 1793
William Stuart Mason, 1795 - March 7,1854
George Mason of Hollin Hall, November 11, 1797 - March 25, 1870
Ann Sarah Stuart Mason, 1803 - November 9, 1852
Mary Elizabeth Mason, ? - February 2, 1885
Edgar Eilbeck Mason, ? - ?
1. Papers of George Mason, I: 679