The four society paragons—Babe Paley, Slim Keith, C. Z. Guest, and Lee Radziwill—celebrated in the FX series Feud: Capote vs. the Swans had much more in common than their tricky friendships with Truman Capote. Each one of them, in their day, dominated the International Best-Dressed List, an honor so rarefied that, like an invitation to Capote’s 1966 Black and White Ball (the subject of Episode Three), no amount of money, publicity, social status, or proximity to “the Tiny Terror” himself could alone secure it.

Paley alighted on the List first, in 1941, the second year of its existence, in second place, while she was still Mrs. Stanley Mortimer, a 26-year-old Vogue editor and navy pilot’s wife. The most universally admired of the foursome, Paley routinely received letters from strangers begging for her hand-me-downs. When she allowed her brunette hair to fade to gray, tied a silk scarf around the handle of her purse, or left a coat’s top button open, thousands duplicated the move. Ambivalent about this unsought attention, Paley informed I.B.D.L. founder (and fellow Black and White Ball attendee) Eleanor Lambert that she feared her daughter, Amanda Burden (likewise a guest and I.B.D.L. honoree), would mistake dressing well for a talent. Lambert replied to her, “Not to worry. It is a talent.”

Paley suited up in Traina-Norell for Vogue’s September 1946 issue.

Paley was also the first of the coterie to be inducted into the I.B.D.L. Hall of Fame, in 1958, the year of its establishment. Capote, who had met her three years earlier, deemed her “the most chic woman I’ve ever known.... I had never seen anyone more perfect: her posture, the way she held her head, the way she moved.”

She was in fact the only member of the Feud squad whom Capote actually designated a “swan,” in his essay in Observations, the 1959 book on which he collaborated with Richard Avedon (another ball invitee). And even then Capote was borrowing the metaphor from 19th-century diarist Patrick Conway, who compared an “aloof armada” of the graceful birds to a convoy of beautiful women.

To costume Paley (Naomi Watts) for the Black and White Ball episode, designer Zac Posen, taking cues from the Castillo sheath she actually wore, found a dead-stock match to the original garment’s zibeline fabric. Babe audaciously lined the creamy dress in scarlet, a detail he preserved, even though producer Ryan Murphy wanted Posen (whom he hired just for the ball scenes) to “tell a story for a contemporary audience, not re-create history,” the designer says. In Posen’s rendition, the red peeking out of the Brancusi-like contours of the gown is meant as “a fun sign of defiance,” he says. “Babe was the Queen Swan of the Pond, and maybe disappointed she wasn’t hosting the evening.”

Slim Keith, Diana Vreeland, then a Harper’s Bazaar editor, and her husband, Reed, ring in 1953 at Kitty Miller’s Park Avenue apartment. Photograph by Slim Aarons.

Slim Keith, then Mrs. Howard Hawks, was next to land on the List, in 1944, climbing to first place in 1946, a period during which Harper’s Bazaar obsessively featured her in half a dozen stories. Although Keith appeared on the List five more times (as opposed to Paley’s 15 total), she was the only one of the quartet who never rose to the Hall of Fame. Dismissive of the fuss made over her wardrobe, Keith demurred: “Just say that I’m a great believer in simplicity in clothes.” Keith’s breezy style, ironically, turned out to have the most longevity. Capote’s Salinas-born “Big Mama” was, by her own estimation, the seminal “California girl.”

Posen adds, “Slim was whip-smart, cutting, 10 steps ahead.” Although he could not find any photos of Keith from the Black and White Ball, her predilection for pants is well documented. “So I put her in a jumpsuit,” he says. Surmising that Keith (Diane Lane) “would have been too cool to wear a party mask,” he gave her large sunglasses instead.

C. Z. Guest (Chloë Sevigny) debuted on the I.B.D.L. in 1952, aged 32, with kudos from Lambert for her “super-distilled blend of debutante and sophisticate,” and entered the Hall of Fame in 1959. Lambert introduced Guest to the esteemed American couturier Mainbocher—a match that proved to be both enduring and mutually inspiring. (She set in motion a mania for his invention, the jeweled cardigan.) “My style,” Guest said, “was his style.”

C.Z. Guest and her equally well-groomed poodle at Villa Artemis, her in-laws’ Palm Beach house, in 1955.

As dressed by Mainbocher, Guest was so understated she was once mistaken for her own maid, and she thought nothing of wearing the same suit for a decade. “Clothes don’t wear out if you hang them up,” Guest reasoned. To evoke Guest’s Yankee polish, Posen imagined her ball dress as “a long glass of milk” with a meringue-like “swish of duchesse satin” in the back, suggesting a jumbo horse-show ribbon.

Then, to offset the patrician glamour of Capote’s “Cool Vanilla Lady,” he added a dash “of Folies Bergère,” in the form of an outsize feathered fan-mask, an allusion to Guest’s rebellious past as a chorine. (Guest’s real-life dress was a subdued black-and-white lace Mainbocher number.)

“Clothes don’t wear out if you hang them up.”

Lee Radziwill, the youngest of the Feud foursome, arrived on the List last, in 1961, trailing on the Cassini coattails of her sister Jackie Kennedy, who became First Lady that year. Although Capote, like Diana Vreeland, considered his “Princess Dear” to have more panache than her sister, she had to wait until 1996, 30 years after the Black and White Ball, to be admitted into the Hall of Fame.

In her sequin-paved column by Mila Schön, Radziwill “seemed to be the only one having a blast at the ball,” Posen remarks. One source of her elation might have been the close presence of the Duke of Beaufort (Hall of Fame 1988), whom Lee called the “sexiest and most elegant” man she had ever known.

Lee Radziwill, dressed in a sequined Mila Schön column, consorts with her host, Truman Capote, at the Black and White Ball on November 28, 1966.

Because Radziwill (Calista Flockhart) was “the most forward dresser” of the flock, Posen envisioned her as a “Futuristic Nefertiti Goddess,” he says. Her mask is historically accurate, but her metallic opera cloak, overlaid with daisy embroidery, is pure fantasy—a signal, he explains, “of the free spirit of the 60s to come.”

As for the unfortunate outsider Ann Woodward (Demi Moore), who in reality never set foot in the ball, Posen dressed her as “a little brave sparrow who wants to be a swan.” The fluttering, Empire-waist, crystal-trimmed chiffon caftan he devised for her was “draped directly on Demi’s body,” he says. “It was a true collaboration.”

According to Capote’s controversial story, “La Côte Basque, 1965,” whose eventual publication precipitated Woodward’s suicide, the erstwhile showgirl “campaigned for the Best Dressed List by lunching with Eleanor Lambert and inviting her for weekends.”

In spite of these alleged efforts, the mariticidal femme fatale, whom Capote nicknamed “Bang-Bang,” failed to be elected to the I.B.D.L. even once. Her wine-and-dine tactics, in any case, would have disqualified her from swandom. The swan’s talent, the author wrote in Observations, “like all talent, is composed of unpurchasable substances.”

Like the bedizened ghost of Capote’s late mother, Nina (Jessica Lange)—who, in Feud, breaches her son’s ball—the true circumstances of the writer’s background interrupt the classic rube-to-riches tale. Though Capote is often portrayed as the hick prodigy who paddled his way upstream from murky southern backwaters to glittering New York high society, Capote in fact spent phases of his troubled, peripatetic youth on Park Avenue and in Greenwich, Connecticut; attended Manhattan’s posh Trinity School; and squired his teen pal Gloria Vanderbilt to the Stork Club and El Morocco.

While the swans, their world, and most of their finery have vanished, Capote’s crystalline prose has not. The otherwise truculent Norman Mailer (another ball guest) got it right. In 1959, the year after Breakfast at Tiffany’s came out, he hailed Capote as “the most perfect writer of my generation, he writes the best sentences, word for word, rhythm for rhythm.”

Amy Fine Collins is an Editor at Large at AIR MAIL. She is the author of The International Best-Dressed List: The Official Story