Five board members of the American Horticultural Society (AHS) who backed the sale of historic River Farm, including the board chair, have resigned, they announced Thursday.

Their departure from the evenly split governing body leaves only members who have opposed selling the Potomac River property that once formed part of George Washington’s Mount Vernon estate.

AHS Board Chair Terry Hayes and the other departing members said in a statement that they were resigning “to allow for the institution to forge a new path forward.”

“The departing Board officers wish the organization well,” the statement said.

The news was celebrated by Northern Virginia elected officials who also had opposed the sale of the property.

“This is fantastic news,” said Fairfax County Supervisor Daniel G. Storck (D-Mount Vernon). “Definitely, the efforts of so many for more than a year have been realized, which is protection, preservation and continuing public access to River Farm.”

The remaining board members issued a statement Thursday thanking their former colleagues for their service. “While we have had our differences about the role of River Farm in future of AHS, we have always shared a commitment to the Society’s overarching goals and mission,” the members said.

Thursday’s resignations come after more than a year of debate and division over how best to protect the property. Two recent offers to purchase the 27.6-acre site ended in stalemate.

One offer came from a private developer who had offered to preserve River Farm as part of a $300 million complex using two contiguous properties that would include a clubhouse, a restaurant, a culinary school and additional housing.

Another came from a coalition of preservationists, led by the Northern Virginia Regional Park Authority (NOVA Parks), that wanted to buy River Farm outright or partner with AHS to ensure public access. The evenly divided AHS board spurned NOVA Parks’ bid during a meeting Sunday, and that vote seemed to be what precipitated the resignations, several participants said.

“They really wanted it to be an amicable thing,” said Leslie Komet Ausburn, who represented Hayes and the departing board members. None of the board members would comment further, she said.

Attorney John T. Richards Jr., who represents AHS board member Laura Dowling, one of the most outspoken critics of the proposal to sell River Farm, called the resignations the “end of the line for this self-inflicted crisis.”

Paul Gilbert, NOVA Parks’ executive director, said his team was already at work on new partnership proposals with AHS that would conserve the land, allow the organization to maintain ownership and maintain its headquarters there, and ensure public access without a sale. He said these goals could perhaps be accomplished with property restrictions and other conservation tools.

“And we’ll see where those proposals go, but I think they’re right in line with the group that didn’t want to sell,” Gilbert said. “It’s a remarkable chain of events.”

AHS’s decision last year to put River Farm on the open market shocked members of the gardening society, angered neighbors, energized political officials at all levels of Virginia government and plunged the nearly 100-year-old nonprofit organization into turmoil.

AHS — which had purchased the site in 1973 with a $1 million gift from philanthropist Enid Annenberg Haupt — said River Farm’s aging manor and grounds had become a financial burden that hindered its educational programs, especially as the pandemic reduced the venue’s revenue from wedding and special events.

Critics, citing publicly available tax returns that suggested AHS was on solid footing, questioned the rationale for selling. Attorneys general in Virginia and the District of Columbia, where AHS is incorporated, opened investigations into whether the sale of the charitable asset was lawful. Even the foundation that executed Haupt’s gift weighed in, saying the sale was counter to the terms of the grant. And departures from AHS’s governing body left two factions that were equal in size and equally dug in, even as negotiations for the sale were underway.

A. Wayne Johnson, an entrepreneur who served in the Education Department for the Trump administration, presented an offer that envisioned preserving River Farm as part of a $300 million complex that would include a top-flight restaurant, small culinary school, additional housing and a clubhouse that would be suitable for weddings and other special events. He offered $20 million for River Farm alone, plus $10 million or more to renovate its 18th-century manor and gardens.

Johnson’s offer triggered alarm inside and outside the organization, and further galvanized the AHS board members holding out against a sale.

“Against the backdrop of this real and present threat, we believe that the efforts to protect River Farm must accelerate,” the five board members said in a letter dated Sept. 26 that was sent to Storck and others and obtained by The Washington Post. The letter called River Farm “an irreplaceable asset of AHS” that should remain in the organization’s hands.

Even as Thursday’s development means AHS’s stalemate has been broken, the remaining members’ stance could create new tensions with members of the community who believe the only acceptable resolution for River Farm is to put it in public hands.

“I think that’s the solution that makes everybody happy,” said Sen. Scott A. Surovell (D-Fairfax). “We’ve all gone through a lot of drama over the past 12 months, and none of us ever want to have to do this again.”