Two years ago, Denise Dennis delivered a dramatic denunciation of Marcellus Shale natural gas development at a Philadelphia City Council hearing. She equated drilling to the tobacco industry, and said that “Pennsylvanians are the lab rats” for a massive shale gas experiment.

The Philadelphia resident had a powerful story – her family owned a historic 153-acre farm in Susquehanna County, Pa., where her ancestors were among the first freed African-Americans to settle in Pennsylvania just after the Revolutionary War. She became a potent symbol in the shale gas wars.

“The process for extracting natural gas from shale is as dirty as coal mining,” she testified to thunderous applause at the 2010 council meeting.

But Dennis’ fervor has subsided in the past two years, undone by the financial need of preserving her family’s deteriorating historic farm, and by the salesmanship of Cabot Oil & Gas.

Earlier this month, Dennis signed a lease allowing the Houston company to extract the shale gas beneath her family’s farm, which the National Trust for Historic Preservation has called a “rare and highly significant African-American cultural landscape.”

“I decided to stop demonizing the industry and to start negotiating with individuals,” said Dennis. “I had to be realistic.”

The reality was that most of the surrounding landowners had leased their mineral rights, and gas drilling was going to proceed with or without the Dennis farm.

“We were an island in a sea of leased land,” she said. “As I saw it, the drilling companies were now my neighbors, and it was better to get along with them than to be antagonistic.”

The lease preserves the Dennis farm by prohibiting Cabot from disturbing the farm’s surface. The company can only extract gas by boring horizontally under the Dennis farm from wells drilled on neighboring land.

Dennis did not disclose the financial terms. But in 2010, she said that gas drillers had offered more than $800,000 for the right to drill. The landowner also receives royalty payments from any gas produced from the property.

The proceeds from the lease will benefit the Dennis Farm Charitable Land Trust, the organization that Dennis set up to preserve the farm that has been in her family for seven generations.

“I am trying to do what’s best for the property,” she said.

The first order of business will be to stabilize the farmhouse, a two-story, timber-framed Cape Cod dwelling built in 1859, which has been unoccupied for more than two decades and is collapsing.

The farm in Brooklyn Township, Pa., now largely overgrown, was pioneered by Dennis’ great-great-great-great-grandfather, Prince Perkins, a black Revolutionary War veteran who moved his family from Connecticut to Northeastern Pennsylvania in 1793. The homestead and the artifacts unearthed there tell a story of free African-Americans who were integrated in a largely white community 70 years before emancipation.

Cabot spokesman George Stark said the company would have been able to develop its surrounding leases without signing up the Dennis farm. But by securing the Dennis lease, Cabot now has the rights under a larger contiguous area, and it can more efficiently exploit the mile-deep Marcellus.

Stark said that the company’s chief executive, Dan O. Dinges, became aware of the Dennis farm’s history and met personally with Dennis in 2011 to assure her the company took her concerns seriously. Cabot also took Dennis on a helicopter tour of its Susquehanna County operations so she could get a sense of its scale.

Dennis was well-versed on the downside of drilling. She had heard stories from embittered landowners in Dimock Township, Pa., five miles from her farm, where Cabot’s gas drilling was blamed for polluting streams and groundwater. Cabot settled with landowners in August.

Her rousing, sarcastic testimony before City Council was widely cited by activists. But afterward, as Dennis began to moderate her position, she stopped attending rallies.

Iris Marie Bloom, the anti-drilling activist who recruited Dennis into the movement, said they are no longer in contact.

“I believe the financial pressures on her were absolutely enormous and the trade-offs painful,” Bloom wrote in an email Tuesday.

Dennis said she was still unconvinced that the hydraulic fracturing process used to extract shale gas is safe. But she toned down the anti-drilling rhetoric as she struggled with the decision.

“Yes, I was vehement,” she said. “But where did that get me? And what would not signing have achieved?

“You don’t get ideal situations in life.”