PHOENIX, ARIZ. - A house designed by Frank Lloyd Wright for his son was sold on Thursday, guaranteeing its preservation after it had been threatened for months with demolition by its owners, who had planned to replace it with new homes.

The deal was closed after at least one offer to buy the property had fallen through. Its former owners, Steve Sells and John Hoffman, principals of a local development company, bought the property for $1.8 million in June and several times raised the price as the controversy over the property's potential demolition intensified.

The buyer's identity has not been revealed; he requested anonymity as part of the transaction. He paid $2.387 million for the house, according to Robert Joffe of Russ Lyon Sotheby's International Realty, who represented the sellers in the transaction. Its latest asking price was $2.51 million. The owners said they had raised the price, most recently by $130,000, to offset the mounting costs of fighting attempts to have the house declared a landmark.

A victory for preservationists around the country, the sale came about through the intercession of the Frank Lloyd Wright Building Conservancy, a group that works to preserve the architect's legacy.

The fight to save the house had galvanized preservationists and stirred spirited debates among Phoenix City Council members over the value of preserving historically relevant structures vs. the need to safeguard homeowners' property rights.

The conservancy and other organizations petitioned the city in June to consider giving the house landmark status after they learned of the former owners' plans to split the lot to build the new homes. Three local government bodies approved the landmark designation, but the council, which has the final say, postponed its vote twice, in part to give the parties more time to strike some type of compromise. There was also uncertainty over how some of its members would vote, given the homeowners' lack of consent for the landmark process.

"If ever there was a case to ... save something historically important to the cultural legacy of the city, this was it," said Larry Woodin, the president of the conservancy.