I've always been an Alfred Stieglitz fan, and in this piece in particular, his influence over Georgia O'Keefe is evident. His unique perspective of the world shaped the direction of her entire career. Its not often that a gallery owner becomes more than simply an agent or lover (of which Stieglitz was both), but also becomes the artistic inspiration and mentor.
Alfred Stieglitz (American, 1864–1946)
From the Back Window, 291, 1915
Alfred Stieglitz Collection, 1949
It too, is also in the Met's permanant collection.