Karl Knaths was born in Eau Claire, Wisconsin, in 1891. He grew up in the Midwest, and in 1912, he moved to Chicago, to study at the School of the Art Institute for four years. In 1913, after seeing the Chicago exhibition of the Armory Show, he was drawn to the Parisian modernist art, especially the work of Paul Cézanne.
His earliest work emulated the Impressionists, but, inspired by local progressive artist– who themselves were influenced by the art scene of Paris– began experimenting with cubism. By the late 1920s, he had made the style his own, creating abstract seascapes and still life subjects.
During the 1930s, Knaths developed a complex theoretical basis for his painting. He began to structure his pictures according to strict rules of composition and color. He was influenced by the ideas of artists like Piet Mondrian and Wassily Kandinsky. Using the color classification system developed by Wilhelm Ostwald, he would preselect the colors for his palette before starting to paint. In Knath's view, color, like music, could be organized according to a system of notation. Each of his canvases, therefore became a unique color composition, since he never used the same arrangement twice.
Throughout his career, Knath depicting the local fisherfolk, docks, shanties, dunes, and moors of Provincetown, as well as objects in his house. As his commitment to Abstraction developed, he was invited to exhibit with the American Abstract Artists group in 1936. He was also a teacher and lecturer, giving annual courses at the Phillips Collection in Washington, D.C. from 1937 until 1950, and was affiliated, at various times, with Black Mountain College and the Skohegan (Maine) School of Painting and Sculpture.
Duncan Phillips, Knaths first and for many years his only patron, did much to establish the artist's reputation. Despite Knath's innovative attitudes, he worked in relative isolation for much of his career, making only the occasional visit to New York or Boston and traveling to Europe.
Knaths died in Provincetown in 1971. Examples of his poetic, Cubist-inspired paintings can be found in the collections of the Metropolitan Museum and the Whitney Museum of American Art in New York, as well as at the Art Institute of Chicago, the Museum of Fine Arts in Boston, and many more. In 1973, a major retrospective of his work was circulated to six American museums by the International Exhibitions Foundation.