Georgia O'Keeffe used charcoal for her influential 1915 abstract series.
In 1915, O'Keeffe created a group of abstract charcoal drawings that reduced natural forms to lines, curves, and rhythmic shapes. The works were radical for their time because they were not conventional studies of recognizable objects. They expressed ideas and sensations through form rather than describing a scene literally.
She sent some of these drawings to Alfred Stieglitz, who exhibited them at his 291 gallery. Their presentation helped launch O'Keeffe's public career and made her one of the first American artists to work in a thoroughly abstract manner.
O'Keeffe later became famous for oil paintings of flowers, landscapes, and bones, so charcoal can be overlooked when discussing her technique. The 1915 drawings were not merely preparatory sketches; they were finished works central to the development of her artistic identity.