A developer plans luxury homes on a beloved Main Line property. But locals are pushing to ‘Save Rock Hill Farm.’

The rolling hills, lush meadows, and verdant woodlands at Rock Hill Farm in Willistown offer glimpses of the past.

They’re also the focus of a battle about the future — not only of Willistown and Chester County, but of once-rural, suburbanizing communities in other collar counties of Philadelphia, where bucolic vistas long treasured by locals are giving way to McMansions and Wawas.

“These large tracts of undeveloped land, these heritage landscapes? Once they’re gone, they’re gone,” said Pennsylvania State Sen. Carolyn T. Comitta, a Chester County Democrat.

Long owned by a conservation-minded local family, Rock Hill Farm was purchased for $25.4 million last December by the high-profile developer and businessman J. Brian O’Neill, who is seeking approval to build as many as 22 luxury houses on portions of the 246-acre property.

Willistown’s Planning Commission is set to vote on his subdivision application Wednesday; if approved, the plan will be scheduled for a review and vote by the township’s Board of Supervisors. Because the application does not request exemptions from Willistown’s zoning regulations, the developer could be able to build the homes by-right.

But supporters of a campaign called Save Rock Hill Farm — who number 350 and counting, according to organizers — said they want to stave off a development they believe will inevitably damage the environment, character, and quality of life in Willistown and beyond.

“We’re just residents of Willistown, Easttown and neighboring communities who are passionate about preserving the benefits of open space for the public at large,” said Les Haggett, a leader of the group whose home in Easttown is across South Valley Road from the O’Neill property. The group has distributed more than 500 “Save Rock Hill Farm” signs and more than 100 matching T-shirts.

Haggett said that although Rock Hill has long been in private hands, its open meadows, woods, and waterways are a local landmark “that lets the environment breathe.” He and others in the group would like the property to become publicly accessible open space and point out that its expanses of undeveloped greenery and scenery already visually connects Willistown’s public Ockehocking and Kirkwood preserves.

“Open space lets people in,” Haggett said. “Development of this nature keeps most people out. ”

He and others said it’s difficult to understand why a township that has supported land conservation since the 1980s would consider a plan to build on one of it largest remaining rural properties. They also point out that Rock Hill contains habitats for birds and other wildlife.

The farm includes a 10-bedroom main house built in 1900, along with several smaller houses, barns, and other structures. The land is home as well to a Crum Creek branch that empties into a reservoir that provides drinking water to Delaware County residents.

“We moved here from the lower Main Line because we believe in open space,” said Michele Cruise, who with her husband, Mark, has lived in Willistown since 2000.

O’Neill and Edmund J. Campbell Jr., the King of Prussia lawyer representing the developer before the planning commission, declined to comment. Members of the Willistown Planning Commission and Board of Supervisors also did not respond to requests for comment.

In a July 7 letter, Campbell presented to the commission three potential approaches to developing the property at South Valley, White Horse, and Grubb Roads.

The first proposal is for by-right construction of five houses on the White Horse section, with 17 additional houses to be constructed on a new cul-de-sac in the property’s 100-acre eastern portion. The developer would retain the right to separately seek approval for additional single-family residential development near the existing main house on the farm’s 122-acre western portion.

An alternative described in the letter includes construction of a single home in the White Horse section and 20 more in the eastern portion. A second alternative calls for construction of 13 houses in the eastern portion and purchase of a $12.5 million conservation easement by a third party to permanently preserve about 75% of the entire property.

“Our preference is to see land in rural areas permanently preserved as open space,” Brian N. O’Leary, executive director of the Chester County Planning Commission, said in an email. An advisory body, the county commission is reviewing O’Neill’s proposals.

“When [total preservation] is not feasible ... we recommend that homes be clustered together with significant open space preservation,” he said in the email, and described proposals to do so as “generally consistent” with the county’s comprehensive plan.

There are 147,000 preserved acres in Chester County, representing 30.2% of its total land area. Willistown had 4,400 acres, or 38% of its land area, preserved, at the end of last year.

“If you’re going to have development,” O’Leary said later during an interview from his office, “then what they [O’Neill’s company] are proposing is pretty good.”

Rising real estate values have continued to spur the sale and subdivision of former estates and upscale farm properties, particularly in Main Line communities.

In June, for instance, Lower Merion Township opted to allow the Linden Hill estate to be subdivided into five building lots.

While higher costs can complicate land preservation efforts, there have been notable recent successes: In April, Westtown Township moved to buy 208 acres of Crebilly Farm for $20.8 million; plans call for the land to become a park.

Meanwhile, the 209-acre Kirkwood Farm property on Providence Road in Willistown was listed for sale last winter in advertisements touting its “endless views” and other attributes.

“To the best of our understanding, the property is under an agreement of sale with a private buyer, and we are hopeful to have a good conservation outcome,” said Kate Etherington, executive director of the Willistown Conservation Trust.

Founded in 1996, the trust uses conservation easements and other tools to protect environmentally sensitive and otherwise significant land in and around Willistown from development by respecting the rights of, and working with, property owners.

The trust has helped conserve 7,500 acres in the headwaters of the Crum, Ridley, and Darby Creeks.

“As for Rock Hill,” Etherington said, “we continue to have conversations with the current owner.”

Interest in maintaining historic, environmentally sensitive, or otherwise meaningful local places and landscapes is nothing new in and around Willistown.

The hamlets of Historic Sugartown and the White Horse Historic District attract visitors. The public can access walking trails on 10 sites that have been protected from development. And a book about Willistown history titled Acres of Quakers, published in 2006 by the township historical commission, ran to 685 pages — and ended in the year 1900.

Save Rock Hill Farm has an active presence on Facebook and elsewhere on social media, and members such as Haggett and Cruise described themselves as newcomers drawn into activism because of the stakes involved.

“Change is good in a lot of ways”, said Rachel Breskman, a member who grew up in Willistown. “But with Rock Hill Farm the [proposed] change is destructive. Not productive.”

Comitta, who serves as minority chair of the Pennsylvania Senate’s environmental resources and energy committee, saluted the grassroots effort.

Land conservation “is a very complicated puzzle” that takes time to get right, she said.

“It’s not linear and it’s not easy. But it can be done,” Comitta said.

“In the case of Rock Hill Farm, I believe it should be done.”

This story has been updated. An earlier version misidentified an opponent of the proposed development. His name is Mark Cruise.