Which teacher encouraged Georgia O'Keeffe's early abstract drawings in 1915?

Arthur Wesley Dow encouraged Georgia O'Keeffe's early abstract drawings in 1915. O'Keeffe studied with Dow at the Teachers College of Columbia University in New York, where his ideas changed her understanding of art.

Dow emphasized composition, line, color, and personal expression rather than simply copying the visible world. His teaching helped O'Keeffe move away from the academic realism she had learned earlier. In 1915, she made a series of abstract charcoal drawings that reduced natural forms to expressive lines and shapes.

O'Keeffe sent some of these drawings to Anita Pollitzer, who showed them to Alfred Stieglitz. Stieglitz exhibited them at 291 in 1916. William Merritt Chase was also important to O'Keeffe as an earlier teacher at the Art Students League, but Chase belonged to her traditional training, while Dow is linked to her decisive turn toward abstraction.