When Frida Kahlo packed for her first trip to the United States, in 1930, she put lots of long skirts in her suitcase. Floor-length skirts had already become the painter’s bohemian uniform by age 23, as she prepared to go to San Francisco with her new husband, muralist Diego Rivera. The colorful garments illustrated her proud Mexican identity while serving a very practical function, too. As a child, Kahlo contracted polio that made her right leg shorter and skinnier than her left; the skirts hid the deformity, with flair.

But even the most brilliantly embroidered floral skirts didn’t fool someone who shared a polio-effected childhood: the discerning documentary photographer, Dorothea Lange. Lange hid her own wizened right leg with wide leg trousers, not skirts, but recognized a shared gait when she first met Kahlo in November 1930.

“[Kahlo] moved in a way that was all too familiar to me,” a fictional Lange narrates in Learning to See, a historical novel by Elise Hooper about the photographer’s life that will be released later this month by Harper Collins. “I watched her cross the marble floor, her long skirt pulling to the right with each step to reveal a slight limp.”

The chance encounter between Lange and Kahlo took place when the Mexican twosome came to San Francisco so that Rivera could compete for mural commissions. One of Rivera’s competitors for the San Francisco Stock Exchange mural happened to be prominent Californian painter Maynard Dixon — Lange’s husband — but this didn’t prevent the two couples from socializing on a few occasions. Rivera was a star, and the whole city seemingly wanted to meet him.

“As Rivera became the toast of San Francisco, the relationship between Kahlo and Lange strengthened,” says Elise Hooper, author of Learning to See. “Kahlo often painted in Lange’s studio to get some space from her husband’s active social life.”

Rivera also gave Lange a few of his drawings of monumental laboring figures, which may have influenced her later Depression-era photographs, such as “Migrant Mother” (1936) — the image for which she is best known. “That Rivera combined artistic genius with passion for the oppressed and exploited was not lost on her,” writes Linda Gordon in her 2009 biography of the artist, Dorothea Lange: A Life Beyond Limits.

But it was when Rivera began a very public affair with his model for the San Francisco Stock Exchange mural that the bond between Lange and Kahlo strengthened beyond their sisterhood of skinny right legs. The photographer’s husband also had a penchant for infidelity, and she, too, was in a marriage of two artists trying to advance their careers. “At this painful moment, Dorothea made a quick and intense connection with Frida: here was a disabled woman of great talent, charm, and political commitment, with a philandering artist husband. Like Dorothea, but twelve years younger,” Gordon writes.

And so, in addition to giving Kahlo use of her studio as a means of creative escape, Lange granted the younger artist an enduring gift: an introduction to a man who would become her lifelong physician and trusted friend, respected thoracic surgeon Dr. Leo Eloesser.

Eloesser was one of Lange’s clients, in addition to being culturally savvy and Spanish-speaking. Kahlo originally saw him because of the chronic pain in her right foot, an ailment for which he suggested rest and a healthy lifestyle (with far more moderate alcohol consumption). As Kahlo’s relationship with Eloesser developed and she shared her history — such as the serious bus accident she had survived at age 18 — he came to know her medical situation more fully.

In gratitude, Kahlo gifted Eloesser a portrait during that first trip to San Francisco. One of her earliest works, she painted a full-length likeness of the doctor at his home at 2152 Leavenworth Street, standing next to a model ship called “Los Tres Amigos” (a reference to the friendship between Eloesser, Kahlo, and Rivera).

Kahlo trusted Eloesser inherently, and kept in touch with him for the rest of her life. Two years after their first meeting, Kahlo wrote to the surgeon from Detroit for a second medical opinion; she was pregnant and wanted to know if her body could carry a child to term. “You have no idea how embarrassed I am to bother you with these questions,” Kahlo wrote, “but I see you not so much as my doctor as my best friend, and your opinion would help me more than you know.” (It is unknown what Eloesser said, but Kahlo kept the pregnancy and soon had a miscarriage that she documented in her 1932 painting, “Henry Ford Hospital.”)

Their correspondence continued, with Kahlo addressing letters to her querido doctorcito (‘dear little doctor’) that included updates on procedures carried out by her Mexican doctors and occasional brags that she had given up drinking (“cocktailitos”), as per his recommendation. She wrote about non-medical maladies as well, and Eloesser was her confidant. “You have no idea what I suffer,” she once wrote to him.

Around 1940, when Kahlo was devastated by her recent divorce from Rivera and in poor health, Eloesser urged her to come to San Francisco for treatment and counseled her to accept Rivera as he was, despite his faults. “[Rivera] has never been, nor ever will be, monogamous,” Eloesser wrote, “[but] Diego loves you very much, and you love him.” Eloesser encouraged her to accept him and remarry. A few months later she agreed, remarrying Rivera in a San Francisco courtroom in November 1940. Kahlo then thanked her friend with another painting, “Self Portrait Dedicated to Dr. Eloesser” (1940), with an inscription to “Doctor Leo Eloesser, my physician, my best friend. With all my love.”

Lange’s referral proved invaluable to Kahlo, and ultimately also fruitful for the San Francisco General Hospital (where Eloesser worked for 36 years). Eloesser owned paintings by both Kahlo and Rivera, which have been displayed in the hospital lobby for 50 years. Eloesser gifted these works to a colleague and close friend, who in turn gave them to the hospital in 1968 with the stipulation that they be publicly viewable. For years, they hung high and barely visible in the lobby; as of a recent renovation completed in 2017, the works now hang prominently at eye level to the right of the guard station.

“Never did a painter, man or woman, so successfully transfer his (or her) emotions to canvas,” Eloesser wrote of Kahlo in his journal. In turn, Eloesser transferred free access to one such canvas to the future patients of San Francisco, the city he and Dorothea Lange called home.