What 1929 object became a recurring subject in Georgia O'Keeffe's paintings?

A cow skull became a recurring subject in Georgia O'Keeffe's paintings from 1929 onward.

While visiting New Mexico, O'Keeffe began collecting and painting animal bones found in the desert. The cow skull became particularly important, appearing in works such as Cow's Skull: Red, White, and Blue and Cow's Skull with Calico Roses.

She treated the skull as a powerful form rather than merely as a symbol of death. Its curved horns, pale surface, and strong silhouette allowed her to combine close observation with broad references to the American landscape and national identity.

O'Keeffe also painted ram skulls, pelvis bones, and other found objects. The frequently reproduced cow-skull paintings should not be confused with her separate series focused on flowers, New York architecture, or the Lake George landscape.