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De Guigne Estate, Hillsborough, Calif.

6. De Guigne Estate, Hillsborough, Calif. (TIE)

List Price: $100 million
Property Size: 47 acres
Listed With: Sotheby's International Realty

Located about 20 minutes south of San Francisco, this 16,000-square-foot Mediterranean mansion was constructed a century ago on land that has been owned by the same family for 150 years. The historic home has a grand ballroom, a flower arranging room, staff quarters that include two chauffeurs’ rooms, and an unusual condition upon which a sale hinges: the owner is requiring that the buyer allow him to inhabit the premises until his death.

America's Most Expensive Homes for Sale

Forbes Staff

To compile our list of the most expensive homes on the market in America right now, we sorted through listings on Realtor.com, Trulia.com, Sotheby’s International Realty, Corcoran Group, Douglas Elliman Christie’s International Real Estate (and its affiliates), Coldwell Banker Previews International, The Agency and others.