Which 1915 series by Georgia O'Keeffe is often described as her first major abstract works?

Georgia O'Keeffe's 1915 Charcoal Drawings series is often described as her first major abstract work.

The series emerged after O'Keeffe rejected the conventional academic exercises she had been producing and began experimenting with simplified lines, curves, and shapes. The drawings were made in charcoal on paper and were not direct depictions of identifiable objects.

O'Keeffe sent some of the drawings to her friend Anita Pollitzer, who showed them to Alfred Stieglitz in New York. Stieglitz exhibited them at 291 in 1916, bringing O'Keeffe into the public modern-art conversation.

The works are sometimes discussed alongside her later abstractions, but Charcoal Drawings is the concise title used for the 1915 group. They mark a turning point from academic realism toward a personal visual language based on abstraction.