In 1964, Baum was approached at the Hyde Park Art Center by artists Jim Nutt, Gladys Nilsson and James Falconer about a group exhibit.

Baum continued to organize notable shows there such as "Nonplussed Some" and "False Image" (1968), and "Marriage, Chicago Style" (1970), with an expanded group of artists.

[23][24] Members of this (also informal) "group" included Ed Paschke, Roger Brown, Christina Ramberg, Barbara Rossi, Irving Petlin, Kerig Pope, and Ray Yoshida, among others.

[25] As an artist, Baum initially focused on painting, but turned to assemblage art, using doll parts and other found objects, in work that was often overtly political, particularly during the 1960s.

[27] Many of them were influenced by psychoanalysis, Baum included: "My dependence on intuition, the sort of experimentation which led to discovering my images...came directly out of that kind of psychoanalytic experience.

[28] Along with Baum, artists in the group included Leon Golub, Cosmo Campoli, George Cohen, Theodore Halkin, June Leaf, Arthur Lerner, Seymour Rosofsky, Nancy Spero, and H. C. Westermann, among others.

[3] Baum participated in exhibitions in the 1960s that criticized and protested the Vietnam War, with works such as his disturbing portrait of then-President Lyndon Baines Johnson, L.B.J.

In 1979, after a period of artistic inactivity, Baum began creating new works after seeing photographs of thatched structures built by boat people from Southeast Asia.

[29] The series, his last key one, called Domus, featured small houses made from disparate elements such as cutting boards, Chinese-checker sets, and paintings of Jesus.

[17] Baum launched the careers of many artists who became nationally and internationally known, and helped establish the notion of a Chicago counter-narrative to the privileged art narratives of his time.

Chuck Thurow, executive director of the Hyde Park Art Center at the time, said, "He had an amazing eye for innovative, new artists that other people hadn't seen.