This series includes five decades of frequent and lengthy correspondence between second-generation Abstract Expressionist painter Helen Frankenthaler (1928-2011) and Sonya Rudikoff. Letters are primarily from Frankenthaler to Rudikoff, numbering around 234 letters and 314 postcards from 1950 to 1997, including several letters addressed to Robert Gutman and the Gutman family after Rudikoff's death. Also present are a few letters addressed to Rudikoff from Frankenthaler's husband, the prominent first-generation Abstract Expressionist painter Robert Motherwell (1915–1991) and his daughters. Motherwell also often signed and wrote postscripts to some of Frankenthaler's postcards throughout the 1960s.

Rudikoff met Frankenthaler, a painter who became widely known for her innovative techniques, including color field painting, post-painterly abstraction, and soak stain, while both women were attending Bennington College in Vermont in the late 1940s. At Bennington, both studied painting with artist Paul Feeley and developed an intimate friendship based on common interests in art and art history. Following their graduation from Bennington, Frankenthaler and Rudikoff shared a New York City studio apartment together in 1950, where Frankenthaler introduced Rudikoff to Robert Gutman, whom she would later marry. During the early 1950s, Frankenthaler carried on a five-year relationship with influential art critic Clement Greenberg, who introduced her to many major figures in the art world and encouraged her to join the Tibor de Nagy Gallery, where she held her first solo show in 1951. In 1952, at age 24, she painted and exhibited Mountains and Sea, which launched her early career. After Rudikoff moved to the Northeast, Frankenthaler sent detailed correspondence about her early paintings and gallery shows, as well as her descriptions of the vibrant New York art scene in the 1950s and 1960s. Throughout their correspondence, but particularly in her letters from the 1950s, Frankenthaler shares, at length, her comments on the direction of contemporary and historical art movements, as well as her opinions of paintings at the many international art shows and galleries she visited. Her letters often contain detailed descriptions of her own work processes and studio spaces, the development of her aesthetic and the evolution of her work over time, her reasons for selecting paintings for various exhibitions, and her reactions to reviews and publicity surrounding her work. They also provide a timeline of her various productive periods and creative lulls, as well as her personal relationships. A small amount of exhibition catalogs and invitations to openings are also present for many of Frankenthaler's art shows.

Frankenthaler married Robert Motherwell in 1958. Afterwards, the couple traveled widely together and resided between New York City, Connecticut, and Cape Cod, where they worked in different studios, often throwing extravagant parties for many well-known artists, critics, and writers. Frankenthaler's letters from this period often describe her impressions of friends, acquaintances, and party guests, including Jackson Pollock, Hans Hofmann, David Smith, Shirley Jackson, Jean Dubuffet, Kenneth Burke, Vladimir Nabokov, Saul Bellow, Peggy Guggenheim, Ralph Ellison, Stanley Kunitz, and Lionel Trilling. In addition to describing her own paintings, Frankenthaler's letters also often include her thoughts on her friends' artwork, including that of her husband, Robert Motherwell, as well as her fluctuating relationship with the New York art scene. Throughout her life, Frankenthaler also wrote regarding her political views, thoughts on aging, international travels, health issues, psychoanalysis, and personal relationships, including her 1994 marriage to investment banker Stephen DuBrul. While Frankenthaler's letters in the 1980s and 1990s are increasingly personal in nature, they still often contain reflections on her career in earlier years, as well as document her later artwork, exhibitions, lectures, and professional service.