Georgia O’Keeffe’s husband Alfred Stieglitz was chiefly known for photography.
Stieglitz was one of the leading figures in the development of artistic photography in the United States. He promoted photography as a serious fine-art medium and published the influential journal Camera Work from 1903 to 1917.
He also organized exhibitions and operated galleries that introduced American audiences to modern art. His photographs of O’Keeffe, made over many years, form one of the best-known visual records of an artist’s life and public image.
Stieglitz worked across photography, publishing, and gallery management, so the question’s answer refers to his principal artistic reputation rather than his full career. He was not primarily a sculptor, architect, or musician.