Of course, Stieglitz influenced and mentored O'Keefe not only through his own works, but also the works of the other artists in his stable.
O'Keefe shaped an entire phase of her early east coast career upon the images the experiences and images she retained from Lake George (where I used to spend my summers as a child). This image from Steiglitz's collection, by Edward Steichen, is the predecessor to this entire phase of O'Keefe's career.
Edward Steichen (American, born Luxembourg, 1879–1973)
The Big White Cloud, Lake George, 1903, printed 1904
Alfred Stieglitz Collection, 1933
Like the others, it too is at the Met.