A broad coalition of Virginia public officials and private citizens has come together to preserve George Washington’s historic River Farm, one of the parcels of land on the Mount Vernon estate. But they say that Washington is only one reason the site is significant.

The site, which the American Horticultural Society (AHS) put up for sale last year, includes archaeological traces of Native Americans who inhabited the land before European contact, the unexplored history of enslaved people, and the little-known story of 19th-century Quakers who migrated to Northern Virginia to demonstrate that slavery was unnecessary. Even the Mathesons — the last family to inhabit Wellington, as the property was also known — were notable figures in Virginia’s history.

The Fairfax County Board of Supervisors is expected Tuesday to vote on altering the property’s zoning by adding a “historic overlay district” that would protect the site. The Planning Commission, following the urging of residents who sent in nearly 100 letters, has already endorsed the measure, which would not prevent development but would allow local officials more control over its use. Gov. Ralph Northam (D) also has signed legislation sponsored by Sen. Scott A. Surovell (D-Fairfax) that would further protect the property and guarantee public access to it.

“Wellington is our history,” Tammy Mannarino, a member of the Mount Vernon Regional Historical Society, told the county’s Planning Commission last month. “It provides an amazingly complete picture of history of the development of our area and the development of Fairfax County from the time of Native American habitation to present day.”

AHS, saying its finances have been weakened by the pandemic, said it needs to sell the property and use the proceeds to build an endowment that would support its national mission of promoting gardening.

In years past, AHS celebrated River Farm’s history and its connection to Washington, often mentioning him when fundraising.

“How fitting that a historic house, cherished by our first President, and for which he hired a foreign gardener, should become the permanent home of the American Horticultural Society,” AHS said in an article in American Horticulturalist magazine after buying River Farm in 1973 with the help of a $1 million gift from philanthropist Enid Annenberg Haupt. “What an obligation A.H.S. has assumed in accepting responsibility for maintaining this property.”

Fairfax County officials said the mission statement changed when the AHS board announced plans to sell the property.

Leslie Kohut Ausburn, an AHS spokeswoman, said the organization has often altered its mission statement and did so before deciding on the property’s sale. She also disputed Washington’s ties to the manor, saying “Contrary to popular belief, none of the structures at River Farm date back to George Washington’s time.”

Fairfax County’s Planning and Development Department has compiled documentation, however, that states the manor was built during Washington’s ownership and substantially modified over the years.

Yet historians say the site’s significance goes back to the earliest human habitation in North America. So far, however, only limited archaeological exploration has occurred at River Farm.

“Certainly, that portion of the Potomac River shoreline has the potential for archaeological resources dealing with every facet of the past regardless of whether it’s Native American history, the invading European histories, or African American enslaved histories,” said Stephen R. Potter, a former National Park Service archaeologist.

The attorneys general in the District and Virginia have opened investigations into the legality of the proposed sale.

In 1987, Fairfax County teachers Martha R. Williams and the late Jack L. Hiller, who offered a special archaeology program for the district, led 22 students on an exploratory dig at River Farm. To protect AHS’s gardens, the scope of the work was limited. But the teachers and their students, focusing on six general areas, turned up evidence of prehistoric habitation that was “quite pronounced,” according to a 43-page report written by Hiller and Williams, who became a professional archaeologist after her retirement.

Among the finds were a white quartz, Halifax-style arrowhead at least 4,500 years old; flakes left by people making stone tools; and a stone tool, classified as a knife or Savannah River-style point, that dates to about 3,000 years B.C., Williams said in an interview.

The students uncovered hand-cut bricks, bits of ceramic and other 19th-century items. There wasn’t sufficient time to explore areas around the manor’s foundation, but Williams wondered in her report whether it might even predate Washington’s ownership.

But the most promising finds occurred on the bluffs, where Indigenous people had likely encamped to take advantage of seasonal shad runs that amazed Capt. John Smith. Smith, who arrived with other Jamestown settlers, explored the Chesapeake Bay and lower Potomac. He saw such an abundance of fish that, unequipped with anything else, he and his men tried netting them with frying pans. (It didn’t work.)

“When John Smith came to the area, he mapped two pretty major Native American villages on the Potomac,” said Jean Marie Cascardi, a professional archaeologist and member of the Friends of Fairfax County Archaeology and Cultural Resources. “So we know in this area there was a lot of Virginia Indian activity at that time.”

Washington swooped in to buy the property in 1760 when he got wind that its owner, William Clifton, was in debt, and he purchased about 1,800 acres for 1,200 pounds sterling. He then gave the land to his aide Tobias Lear to use.

Though often identified only as Washington’s secretary, Lear was an important person in his own right who also carried out state duties for Presidents Thomas Jefferson and James Madison, including negotiating a peace treaty with a Barbary pirate, said Ethel R. Eaton, a former archaeologist with Virginia Department of Historic Resources. His firm, T. Lear and Co., occupied a riverfront property, including a wharf, where the Kennedy Center now stands, and he contributed to efforts to build the ill-fated Patowmack Canal.

After Lear’s death, the land passed to Washington’s heirs, who sold it in the 1850s to members of a Quaker colony, opening an early chapter in the South’s struggle for racial justice.

Quakers had begun migrating to Northern Virginia from the North in the 1840s, lured by inexpensive land and fired by the abolitionist spirit. They wanted to demonstrate to Southerners that farming could be profitable without enslaved labor.

Mannarino’s Backyard Mount Vernon blog details the Quakers’ impact. It also tells the story of three brothers — Isaac, William and Stacey H. Snowden — who purchased parcels of River Farm and occupied several notable homes along the Potomac. Stacey Snowden, who helped establish one of the first public schools in the 1870s, also became Mount Vernon’s supervisor on the Fairfax County Board of Supervisors, which was created in 1870.

By the early 20th century, River Farm fell into a state of disrepair. In 1919, it was purchased by Malcolm Matheson, who was heir to a fortune. Matheson added a ballroom, a swimming pool, a tennis court and essentially grafted a Colonial Revival-style mansion onto the existing structure. He filled its gardens with boxwoods, wisteria, magnolias and other ornamental plants.

His son, Malcolm Matheson Jr., became a prominent Northern Virginia developer whose firm helped construct the CIA building in McLean and the Mount Vernon visitors center.

But the story most overlooked and in need of telling concerns enslaved peoples there, historians said. Washington inherited enslaved people as a boy, and when he married Martha Custis, he joined the ranks of Virginia’s largest enslavers, Matthew R. Laird, an archaeologist who surveyed the River Farm area for the National Park Service, said in his report.

By the 1790s, Washington recorded upward of 57 enslaved people living at River Farm, which then encompassed much more than what’s left of the site now. It’s not clear whether some lived on the property that’s left now by that name, but until recent decades, few archaeologists bothered to look.

“Early archaeology looked at the — I’m using air quotes here — ‘important people’ but not the rest of the people,” Cascardi said. “It’s definitely something that has garnered a lot more attention in the last 30 years.”