The first important school of American painting to be developed independently of European styles of art is called Abstract Expressionism.

The term Abstract Expressionism is the collective name for the work of a heterogeneous group of New York artists who produced vivid, emotionally charged non-representational paintings characterized by very bold uses of color and mass. The term abstract expressionism was used in 1929 by Alfred H. Barr, Jr., founder of the Museum of Modern Art in New York, in reference to the early improvisations of Wassily Kandinsky. In 1946, Robert Coates, art critic of The New Yorker magazine, employed it in relation to a group of paintings done in New York. The term was popularized during a series of discussions that took place in 1952 at the "Club" on Eighth Street in New York City among a number of painters and sculptors; during the sessions, the artists themselves rejected it as an unsatisfactory indicator of their art. Although the term, along with others used to refer to the art that developed in New York during the 1940s – action painting, the New York school, and American-type painting is in many ways misleading, it has remained the predominant one in discussion of this art. Abstract expressionism is not a unified artistic style; what the artists who promulgated it had in common was the search for a significant subject in an abstract format. They sought a format that could express their individual personalities and at the same time could lead to the expression, through the process of painting, of a universal, timeless content.

During the 1930s many of these artists had worked on the Federal Art Project under the Works Progress Administration. Some had come in contact with Hans Hofmann, already an influential teacher of modernist theory in New York City. The majority had been exposed to various modernisms (such as Constructivism, Dada, Surrealism  and the work of Paul Klee and Kandinsky) through gallery and museum shows, and most had grappled with Cubism, specifically in the then overwhelming person of Pablo Picasso. In 1937, John Graham's influential book System and Dialectics of Art was published, and his ideas on the prominence of the subconscious, based on the theories of Sigmund Freud and C. G. Jung, were already becoming an important topic of conversation. Willem De Kooning and Arshile Gorky, then close friends of Graham, were already showing a shift in style and direction. By the end of the 1930s, a few small groups of painters in New York City were expressing their dissatisfaction with the current, prevalent trends of social realism and geometric abstraction (as exemplified by the group called American Abstract Artists). During the next few years many prominent European modernist artists such as Andre Breton, Max Ernst, Fernand Leger, Andre Masson, and Piet Mondrian immigrated to New York to escape the war in Europe. Their arrival reinforced the American artists, who were politically conscious of, as well as schooled in, modernist art theory, Freudian and Jungian psychology, existentialist philosophy, theories of symbolist poetry, and Oriental art and ideas. They also knew the work of Milton Avery, Arthur Dove, and the group shown by Alfred Stieglitz at his American Place Gallery, the most avant-garde artists of that period in the United States.

During the early 1940s, two important groups of artists were actively meeting and discussing an art that combined mastery of painterly values with psychologically intense content, and thus expressed universal human emotions appropriate to the tragic climate of World War II.  In 1941-42 the American artists William Baziotes and Robert Motherwell, along with the Chilean surrealist Matta Echaurren, were discussing such ideas; they were soon joined by Jackson Pollock and Lee Krasner.  They based their work on surrealism's generative principle of "psychic automatism" but differed from the Europeans in their equal regard for the process of painting, for the plastic qualities of the painterly medium. At the same time, Adolph Gottlieb and Mark Rothko, soon joined by Barnett Newman and Theodoros Stamos, were advocating the use of ancient mythology and primitivizing content in their similar efforts to forego current aesthetics. Separately and simultaneously, other artists such as Clyfford Still, Richard Pousette-Dart, and Ad Reinhardt were evolving their art of parallel ideas. By the mid-'40s these artists had discovered their unique painting approach, one that placed them at the forefront of abstract painting at midcentury. By the end of the decade, they were moving apart; interrelationships, although intense, were always tentative, largely because of the individualistic nature of their art.

The abstract expressionists are usually divided into two groups: the "gestural" wing includes Gorky, de Kooning, Hofmann, and Pollock; the "color-field" wing, Gottlieb, Newman, Rothko, and Stamos. Any such classification, however, is an oversimplification. Even though the abstract expressionists benefited mutually during their formative years of the 1940s, in the end they must be considered separately, as painters who always work toward the universal via the personal, striving to convey a timeless and deeply emotional human content through abstract form.