In My Way of Life (1971) Joan writes:

Billy [William Haines] helped me with the home Alfred Steele and I created in New York. It was a very special place, occupying the top two floors and overlooking Central Park. Originally it had eighteen rooms. We broke them down into eight large ones, with huge windows. I wanted to bring a California ambience with me so we picked bright colors and built in lots of the conveniences that aren't so common in the older buildings in New York. There was a marvelous free-flying staircase, and the wall alongside it was punctuated with large green plants. At the top was a skylight. Sunlight permeated the whole apartment and was refracted by the white carpet. Even the room we called the office was in light, gay colors. There wasn't a dark nook in the whole place--except possibly the broom closet.

There were large raised fireplaces in the drawing room and bedroom, and a working fountain in the two-level bedroom. Curtains, draperies, and upholstery were all hand woven....

 When Alfred and I started planning the Fifth Avenue apartment, he said, "You just go ahead. After all, it's your home."

"No," I said. "It's our home. I want you to be happy in every room. I don't want you to go from one room to another unhappy with one single piece of furniture, or one color."

So he was consulted about every item. Every piece of furniture was made to order for its special place. He wanted a bright green carpet for his study, and agreed with me on pink for our bedroom. How I adore pink!

In designer Carleton Varney's 1980 book There's No Place Like Home, he writes of seeing Joan's Fifth Avenue apartment for the first time in late 1965 (he had been invited to see how Joan lived before he assisted her in decorating her next apartment at Imperial House):

Her entire apartment had been architecturally planned and designed by Skidmore, Owings and Merrill. Her late husband Alfred, whom she once described to me as the only man she ever loved, had added the second floor to the penthouse to make room for a bedroom befitting a superstar. The apartment was extraordinary. The floor was pink marble, like the inside of an exquisite shell, and the view of Central Park framed by an all-glass wall was spectacular. As we walked from room to room I thought about what this space represented: Fifth Avenue in the 70s, high above the greatest city in the world, a view that spanned a panorama of the park from the Plaza Hotel on the left to the Metropolitan Museum on the right....

The late William Haines, a friend of Joan's who had been in films before he turned to interior design, had been the creator of Joan's penthouse, and the decor throughout was like a movie set built in New York: blond modern 1950s Beverly Hills glamour, but expensive. Billy Haines had very costly tastes, even for those fat years, and when he did Joan's penhouse he had apparently indulged his most expensive decorating fantasies. The result was a sort of "Hollywood Rises Over Central Park." The rooms were filled with long sweeping sofas and silk upholstered chairs with legs that angled out in a crazy way. All the furnishings were covered in lemon yellow, beige, or white biscuit-quilted fabrics, and everywhere I looked the furniture was covered in clear plastic... This first look at her penthouse was also my introduction to Joan's obsessive tidiness. The lady wanted everything in her life to be clean!

And neat! In the dining room an enormous table was bolted to the floor and surrounded by cabinetry that opened discreetly at the touch. Joan had storage space everywhere for her silver, dishes, porcelains, and accessories. There was an entire room for shoes and another for hats. As I walked through the rooms I was impressed by a feeling of order, spartan cleanliness, and an absence of flamboyance, even of bright color. It was an austere place that didn't fit the personality of the owner, I thought.

Her bedroom was another matter. All the bedrooms I was to design for her featured pink and white, the colors of that penthouse bedroom, for she thought that color scheme was very flattering. Alfred Steele's bedroom, which was next to Joan's, had not been altered since his death [in 1959]. If the rest of the apartment had been decorated in Hollywood Modern, Alfred's bedroom had been done in Hollywood Motel. Again the furnishings were blond 1950s vintage, and the Hollywood bed had fitted covers and a bolster back upholstered with gold Lurex threading its glistening way through a black material. The wall-to-wall carpeting was emerald green, and the pillow accents on that Hollywood bed were bright, bright yellow and orange. For a chairman of the board of Pepsi-Cola, the room was a shocker...On that same floor, along with the room for shoes and the room for hats, was a massage room where Joan lay on a big table to get her daily massage...

Upstairs, downstairs, and all over the apartment were those white rugs...