Georgia O'Keeffe used charcoal for the 1915 abstract series that launched her mature style.
While teaching in South Carolina, O'Keeffe made a group of radically simplified charcoal drawings. The works translated natural forms and sensations into lines, curves, and tonal relationships without directly depicting recognizable objects. She sent some of the drawings to a friend, who showed them to Alfred Stieglitz.
Stieglitz exhibited the drawings at his New York gallery in 1916. Their presentation marked an important breakthrough because O'Keeffe was then experimenting with abstraction before it was widely accepted in American art. Her later practice included oil, watercolor, pastel, and other media, so charcoal was not her only medium; it is specifically associated with this breakthrough series.