Mason died in Alexandria on December 21, 1838, at the age of 53, survived by his widow and several children. Mason's widow Betsey completed Colross and remained active in the community, including as the Vice-Regent for Virginia of the
Mount Vernon Ladies Association (which secured a contract to acquire Mount Vernon in 1858). Two decades after Mason's death, his widow unsuccessfully attempted to sell Huntley and its accompanying Hunting Creek farm.
Arthur Pendleton Mason, who married a daughter of Justice
John Archibald Campbell and became a Confederate officer during the American Civil War, inherited and lived at Colross. He sold it to the locally prominent Smoot family, which used it as their business office as well as continued to entertain at the house. However, between 1929 and 1932, that large and historic Georgian style house was physically moved brick by brick to
Princeton, New Jersey, to permit further commercial development of the 1100 Oronoco Street block which it had occupied. In 1958 the rebuilt structure was sold to the
Princeton Day School, which currently uses it as an administrative building. In 2005 the City of Alexandria authorized an archeological survey of the site, which unearthed a cistern and evidence of slave residences, among other structures. In 1989, the
Fairfax County Park Authority acquired Huntley. The restored main house is open for regular tours on Saturdays, April through October, and hosts special programs and events. Renovation of the nearby tenant house was completed in 2017 and it is used as a visitor welcome center for tours and programs. ==Marriage and children; relations and ancestry==