Kline, along with other action painters like Jackson Pollock, Willem de Kooning, Robert Motherwell, John Ferren, and Lee Krasner, as well as local poets, dancers, and musicians came to be known as the informal group, the New York School.

[5] He spent summers from 1956 to 1962 painting in Provincetown, Massachusetts, and died in 1962 in New York City of a rheumatic heart disease, ten days before his 52nd birthday.

Many of the figures he depicted are based on the locomotives, stark landscapes, and large mechanical shapes of his native, coal-mining community in Pennsylvania.

From the late 1940s onward, Kline began generalizing his figurative subjects into lines and planes which fit together much like the works of Cubism of the time.

[8] In 1946, the Lehighton, Pennsylvania, Post of the American Legion commissioned Kline to do a large canvas depicting the town where he had attended high school.

[9] It is widely believed that Kline's most recognizable style derived from a suggestion made to him by his friend and creative influence, Willem de Kooning.

However, even though Willem de Kooning recalls that Kline delved into abstraction "all of a sudden, he plunged into it", he also concedes that it took considerable time, stating that "Franz had a vision of something and sometimes it takes quite a while to work it out.

[13] Kline's first one-man show took place between October 16 and November 4, 1950, at the Egan Gallery, 63 East 57th Street, and consisted of eleven abstract paintings.

[14] In the early 1950s, his work appeared very much inspired by French painter Pierre Soulages, who had exhibited in Betty Parsons' gallery in New York in 1949.

[15] In the late 1930s in London, Kline had called himself a "black and white man", but not until the Egan Gallery show had the accuracy of this phase become clear to others.

[12] In the late 1950s, in such paintings as Requiem (1958), Kline began experimenting with more complex chiaroscuro instead of focusing on a strict monochromatic palette.

Kline carefully rendered many of his most complex pictures from extensive studies, commonly created on refuse telephone book pages.

Unlike his fellow Abstract Expressionists, Kline's works were only meant to look like they were done in a moment of inspiration; however, each painting was extensively explored before his housepainter's brush touched the canvas.

[22] In 2012, San Francisco financier George R. Roberts sold a nearly ten-foot (3 m) wide, untitled black-and-white work from 1957 at Christie's, New York.

[26] The project, which presents for the first time an online compendium of Kline's oil on canvas works made between 1950 and the artist's death in 1962, was completed in 2022.