Although Georgia O'Keeffe (1887-1986) has long been celebrated as a central figure in twentieth-century art, the abstract works she created throughout her career have remained overlooked by critics and the public in favor of her representational subjects. In 1915, O'Keeffe leaped into abstraction with a group of charcoal drawings that were among the most radical works of art produced in the United States at that time. In these and subsequent abstractions,...