Colross (also historically known as Belle Air and Grasshopper Hall) is a Georgian style mansion built around 1800 as the center of a large forced-labor farm in the Old Town neighborhood of Alexandria, Virginia, and moved circa 1930 to Princeton, New Jersey, where it is currently the administration building of Princeton Day School.
The Colross property originally occupied the entire 1100 block of Oronoco Street; Alexandria merchant John Potts developed it as a plantation and began building the mansion in 1799–1800. In 1803, Jonathan Swift—also an Alexandria merchant and a city councilman—purchased the property and during his ownership continued constructing the mansion. After Swift died in 1824, Colross was purchased by Thomson Francis Mason (1785–1838), son of Thomson Mason (1759–1820) and grandson of Founding Father George Mason (1725–1792) of Gunston Hall. Mason served as a judge of the Criminal Court of the District of Columbia and as mayor of Alexandria. Mason, who made Colross his chief homestead, modified and enlarged the mansion. After successive ownerships, the area around Colross became heavily industrialized. The mansion was bought by John Munn in 1929; between that year and 1932, it was transported brick-by-brick to Princeton, where in 1958 it was sold to Princeton Day School, which uses it as a school administration building housing its admission and advancement offices.
The Colross mansion is a two-story, brick, Georgian-style structure that features an architectural plan similar to that of Mount Vernon and Woodlawn, and it was originally flanked by two wings. The front entrance is covered by a spacious Neoclassical portico that is supported by wooden Doric columns. The roof is topped by a balustraded deck and is further embellished by three dormer windows.
In 2005, after the original Colross site was purchased by a real estate development company, the city of Alexandria requested an excavation by archaeologists, who uncovered an underground domed brick cistern, evidence of slave outbuildings, the foundations of the estate's peripheral walls, and several ancillary structures.
Colross served as the venue for several significant Mason family events, including the wedding ceremonies of Thomson Francis Mason's daughters Sarah Elizabeth Mason (1819–1907) and Virginia Mason (1830–1919). According to local tradition, two children in the Mason family died on the property and were interred in the estate's burial vault. Successive owners of the Colross estate claimed it was haunted by the deceased Mason children.
The land on which Colross was first located was originally part of the Northern Neck Proprietary, a land grant that the exiled Charles II awarded to seven of his supporters in 1649 during the English Interregnum. Following the Restoration in 1660, Charles II finally ascended to the English throne. Charles II renewed the Northern Neck Proprietary grant in 1662, revised it in 1669, and again renewed the original grant favoring original grantee Thomas Colepeper, 2nd Baron Colepeper and Henry Bennet, 1st Earl of Arlington in 1672. In 1681, Bennet sold his share to Lord Colepeper, and Lord Colepeper received a new charter for the entire land grant from James II in 1688. Following the deaths of Lord Colepeper, his wife Margaret, and his daughter Katherine, the Northern Neck Proprietary passed to Katherine's son Thomas Fairfax, 6th Lord Fairfax of Cameron in 1719.
John Potts, a prominent Alexandria merchant, developed the Colross property as a forced-labor cash-crop farm. He began building a brick mansion on the property between 1799 and 1800. Potts encountered financial difficulties and placed the unfinished mansion on the market in 1801. In December 1803, Jonathan Swift, a merchant and Freemason, bought the property for $9,000. Swift purchased Colross for his bride, Anne Roberdeau, daughter of Brigadier General Daniel Roberdeau (1727–1795). Some sources say Swift's wife reportedly named the estate Belle Air; according to other sources, Swift referred to his estate as both "Belle Air" and "Grasshopper Hall". Swift presided over Alexandria City Council from 1822 through 1823. His wife, two daughters, and three sons lived with him at the mansion. As Alexandria expanded, Colross evolved from a rural plantation into an urban estate. Between 1791 and 1847, the city of Alexandria was a part of Alexandria County within the District of Columbia.[ Swift continued to construct the mansion. After his death in 1824, the estate transferred to the ownership of Lee Massey Alexander and his sister, Mrs. Chapman. The Alexander family owned the estate for a brief period; they renamed it "Colross".
Colross was then purchased by Thomson Francis Mason (1785–1838), a prominent jurist, lawyer, councilman, judge of the Criminal Court of the District of Columbia, and mayor of Alexandria between 1827 and 1830. Mason was the eldest son of Thomson Mason (1759–1820), and was the grandson of U.S. Founding Father George Mason (1725–1792) of Gunston Hall. According to Mason's daughter Virginia Mason Davidge, her father won Colross "at a game of cards" from Lee Massey Alexander. Mason used Colross as his chief homestead and made substantial modifications and additions to it. Mason built a 10 ft (3.0 m) high brick wall around the exterior of the Colross property. Around the same time Mason acquired Colross, he built Huntley in Fairfax County, Virginia as a rural retreat and summer villa. Mason's son, Arthur "Pen" Pendleton Mason (1835–1893), later inherited the Colross estate. Pen Mason was married to Mary Ellen Campbell, a daughter of John Archibald Campbell (1811–1889), an Associate Justice of the Supreme Court of the United States. Orlando B. Willcox, who later served as a Union Army general, visited Colross on several occasions around 1851; he described it as a "fine house and ground and the chief residence of the Masons of Alexandria, much frequented by officers of the army". Willcox also remarked on the "hospitality and civility of the head of the house", Pen Mason's mother, Elizabeth "Betsey" Clapham Price (1802–1873).