Alfred Stieglitz’s New York gallery was known as 291.
The name came from the gallery’s address at 291 Fifth Avenue. Stieglitz opened the space in 1905, initially as the Little Galleries of the Photo-Secession, before it became widely known by its street number. It showed photography and avant-garde European and American art.
O’Keeffe’s work entered Stieglitz’s orbit through exhibitions connected with his gallery. He first exhibited her abstract charcoal drawings in 1916, helping bring her work to the attention of New York’s art world.
291 is sometimes confused with two later Stieglitz galleries, the Intimate Gallery and An American Place. Those names refer to different spaces and periods. The concise number 291 specifically identifies the Fifth Avenue gallery that became a landmark for early American modernism.