Richard W. B. Feigen, an architect who bought No. 634 in 2006, said he had gotten such calls. “This agent has been flirting with me,” he said. “Now I know how pretty girls feel.”

He said he was not thinking of cashing out. “I’m a preservationist by nature,” he said. “One of the first books I was given was called ‘Holdouts!,’ about all these buildings in New York City where people would not sell to developers, so they had to build around, an office building with a notch where there was a house where the owner wouldn’t sell.

“I felt proud of those people,” he said. “I never thought I’d be in the same position. If I were to sell my house, then the four houses up the hill would be relevant to the developer because he can’t connect to those four houses without mine.”

Loretta Keeling, who with her husband, Marshall, owns No. 638, said she, too, had been inundated with calls about selling, so much so that she had referred them all to her son. She would not say whether the family had any plans to sell, but she said she was “conflicted” about whether the row of houses should receive landmark designation.

“Frankly, I thought it should have been included when they first did it,” she said, “and the fact that they want to include it now is more due to the fact that there are several houses that are vacant and I presume up for sale.” She and her husband have lived there for 43 years.