Before the spies came, the house was perfect.

Five thousand square feet, wide windows, a grand staircase, a front porch with a panoramic view of nature. The year was 1933, and Northern Virginia was still the countryside, even with Washington just across the Potomac. So it was the ideal retreat for Florence Thorne and Margaret Scattergood, two pioneers of the American labor movement who defied the gender expectations of their time.

“Florence said, ‘Of all the houses we looked at, this is the only one I would care to live in,’ ” Scattergood recalled years later. “That was pretty final.”

The women lived at the estate for a decade before it appeared that some federal agencies were also looking to buy property across the Potomac. And they wanted the land where the big white house sat.

In 1948, Thorne, 71, and Scattergood, 54, made a deal: They would sell their 30 acres to the government, but only if they could live out the rest of their lives in their home. Any agency that acquired the land would have to abide by that agreement.