What was Georgia O'Keeffe's first widely recognized abstract series made in 1915?

Georgia O'Keeffe's first widely recognized abstract series was her group of charcoal abstractions made in 1915.

While teaching art in South Carolina, O'Keeffe began producing radically simplified drawings in charcoal. They did not depict recognizable objects; instead, they used flowing lines, geometric structures, and tonal contrasts to explore visual relationships. She sent some of these drawings to her friend Anita Pollitzer in New York.

Pollitzer showed them to Alfred Stieglitz, who exhibited them at his gallery 291 in 1916. This brought O'Keeffe to the attention of New York's modernist circle and made her one of the first American artists to work in complete abstraction.

The charcoal drawings were not her only abstract works. She later used watercolor and oil and returned to abstraction throughout her career. The phrase “charcoal abstractions” identifies the breakthrough 1915 group, rather than a later named subject series.