Alfred Stieglitz's New York gallery was called 291, after its address at 291 Fifth Avenue.
Stieglitz operated the gallery from 1905 to 1917. It became an important venue for modern art and photography, showing European artists alongside American artists such as Georgia O'Keeffe.
O'Keeffe's work was first shown there in 1916 after Anita Pollitzer brought Stieglitz some of her charcoal drawings. The exhibition helped establish her public reputation before she moved to New York permanently.
The name 291 is often confused with Stieglitz's later gallery, An American Place. That later space operated from 1929 until his death in 1946, whereas 291 closed during World War I.