In addition to his mural work for various American government projects, he was an innovative independent painter and university art professor.

[2] After viewing an exhibit of abstract art, Kelpe, who had previously wanted to become a musician, decided instead to pursue a career as a painter.

[7] His work of this period depicted hard-edged planes and shapes which overlapped and interpenetrated,[2] and he conceived of his paintings as an "organization of forms, not objects of nature".

[6] In the early 1930s he moved on from this assemblage technique; rather than incorporating physical objects into his works, he instead began painting mechanical parts such as wheels and gears into his abstractions.

[3] As this project was largely concerned with American scene painting and was not open to abstract art, Kelpe included representational images such as buildings and wheels in his designs.

His images, products of his imagination rather than any real world industrial site, incorporated a balance of shapes in various sizes and colors.

[7] Feeling stifled by the attitudes so strongly favoring realist art, and desiring an atmosphere which would be more accepting of his abstract sensibilities,[7] Kelpe relocated to New York in about 1935.

[11] Kelpe's detailed murals, which include various geometric shapes such as triangles, rectangles, trapezoids, and circles, differ from the others in the project by their unique color juxtapositions, their striped, gridded, or bubbled patterns, and their sculpture-like structures.

[5][12] A critic for New York magazine writes that Kelpe's work "looks best of all; his allegiance to Synthetic Cubism may have weighted favor against him at the time, but now his pair of canvases seem masterly in their subtle balance of oranges and greens, and their purely abstract hints of Picassoid guitars – real jazz-age exuberance.

Although the group sought to engender acceptance of abstract art by the public, critics within the ranks of the organization disapproved of Kelpe's "spatial illusionism", whereby his geometric shapes appeared to float in three-dimensional space.

The inspiration for his technique may be traced back to his exposure while still a student in Germany to the Russian and German Constructivists such as Kandinsky, Lissitzky, and Schwitters.

[2] He experienced financial hardship in the 1950s, writing that his circumstances were hopeless, and that he couldn't afford to both pay the rent and purchase food.