She was born Alice Christmas on Oct. 26, 1923, in Philadelphia “to a bourgeois family of color,” as she wrote in an unpublished memoir. Her father, Lawrence Duke Christmas, was a dentist; her mother, Alice (Meyers) Christmas, managed the household. In Alice’s telling, the family was so light-skinned that they were known as the White Christmases.
Yet Alice’s world was circumscribed and sheltered, she said, and she didn’t interact with any white people until she attended Colby College, in Maine. It was her race-conscious mother who decided that Alice should “pass” and live her life in the white world, so as not to face the era’s prejudices toward people of color. Her mother arranged a marriage with a light-skinned cousin named Joe Christmas. Joe was not keen on passing, however, and Alice was not keen on marriage — hence the divorce. By the late 1940s, she had moved to New York City, knowing no one there.
She soon christened herself Alice F. Mason. She liked the actor James Mason, and the F stood for Fluffy, an incongruous nickname given to her by Mr. Vanderbilt because she was anything but. It was also a potent combination of letters, in numerology terms.
Ms. Mason’s secret came out in 1999, when her family ties were noted in “Our Kind of People: Inside America’s Black Upper Class,” by Lawrence Otis Graham. But it was hardly a bombshell. No one seemed to notice or care. “There are many people with family members who live on both sides,” Ms. Mason told New York magazine. “I’ve led this life for over 45 years, and it’s all a state of mind.”
In addition to her daughter, she is survived by a grandson.
Ms. Mason closed her firm in 2009, when she was 86. The rich no longer needed her specialized knowledge. Park Avenue, with its fussy, archaic rules, had ceded much of its cachet to the glassy new condos being built downtown, to which the ticket for entry was simply money.
She never left the rent-stabilized apartment where she held her storied dinners, in a century-old building on East 72nd Street. (In Manhattan real estate parlance, it was a classic eight, a gracious prewar layout that included three bedrooms and two maid’s rooms.) In 2011, the developer Harry Macklowe bought the building for a reported $70 million and began to turn the units into condos, buying out the tenants to do so.
But Ms. Mason refused to give up her apartment. When she moved there in 1962, the rent was $400 a month. At her death, it was $2,476. The apartment below her, in the same line, was recently on the market for just under $10 million.