Sleigh painted group portraits of the artists in both organizations. The SoHo 20 Gallery Group Portrait was painted in 1974. Her A.I.R. Group Portrait (1977–78) is considered to be a document of the feminist movement, especially the centering of women in cooperative galleries. Among the feminist artists in A.I.R. Group Portrait are Nancy Spero, Howardena Pindell, Agnes Denes, Sari Dienes, Blythe Bohnen, Dotty Attie, and Mary Beth Edelson. Sleigh painted herself standing next to Howardena Pindell. Between 1976 and 2007, Sleigh painted a series of 36-inch portraits which feature women artists and writers, including Helène Aylon, Catharine R. Stimpson, Howardena Pindell, Selina Trieff, and Vernita Nemec. In a 2007 interview with Brian Sherwin, Sleigh was asked if gender equality issues in the mainstream art world, and the world in general, had changed for the better. She answered, "I do think things have improved for women in general there are many more women in government, in law and corporate jobs, but it's very difficult in the art world for women to find a gallery." According to Sleigh, there is still more that needs to be done in order for men and women to be treated as equals in the art world. During the last two decades of her life, Sleigh purchased or negotiated trades of over 100 works of art by other women and exhibited her growing collection at SOHO 20 Gallery in 1999. These included paintings, sculptures, and prints by Cecile Abish, Dotty Attie, Helène Aylon, Blythe Bohnen, Louise Bourgeois, Ann Chernow, Rosalyn Drexler, Martha Edelheit, Audrey Flack, Shirley Gorelick, Nancy Grossman, Pegeen Guggenheim, Nancy Holt, Lila Katzen, Irene Krugman, Diana Kurz, Marion Lerner-Levine, Vernita Nemec, Betty Parsons, Ce Roser, Susan Sills, Michelle Stuart, Selina Trieff, Audrey Ushenko, Sharon Wybrants, and many others. In 2011, the Sylvia Sleigh Collection was donated to the Rowan University Art Gallery and forms the core of its permanent collection. Invitation to a Voyage In 2006, Sylvia Sleigh donated her largest painting, Invitation to a Voyage: The Hudson River at Fishkill (1979–1999), to the Hudson River Museum. In fourteen panels totaling 70 feet in length, Sleigh's panorama occupies two walls when exhibited. She was inspired by the pastoral works of Antoine Watteau, Giorgione, and Édouard Manet. Included are Sleigh's husband, Lawrence Alloway, and a group of friends who were mostly artists and art critics. They are picnicking, posing, painting, and interacting against the backdrop of