Georgia Totto O’Keeffe (November 15, 1887-March 6, 1986) was an American artist best known for oil paintings characterized by sophisticated gradations of tone and color.
Biography on Wikipedia: https://en.wikipedia.org/wiki/Georgia_O%27Keeffe
The Shelton with Sunspots, N.Y. by Georgia O’Keeffe
1926 / Oil on canvas / 48-1/2″x30-1/4″ / Art Institute of Chicago, IL
Georgia O’Keeffe on Artnet: http://www.artnet.com/artists/georgia-okeeffe/