Alfred was a big promoter of photography, and creator of the first photography magazine “camera work” 
His celebrated portrait of Georgia O’Keeffe (1997.61.19) was one of his chief occupations between 1917 and 1925, during which time he made several hundred photographs of the painter (who became his wife in 1924). 
His refusal to encapsulate her personality into a single image was consistent with several modernist ideas: the idea of the fragmented sense of self, brought about by the rapid pace of modern life; the idea that a personality, like the outside world, is constantly changing, and may be interrupted but not halted by the intervention of the camera; and, finally, the realization that truth in the modern world is relative and that photographs are as much an expression of the photographer’s feelings for the subject as they are a reflection of the subject depicted.
PDFs of Camera Work issues: (very awesome)
Not only were photographs shown at his “291” gallery but paintings and other art as well (Picasso paintings, et al)
Camera Work, where Gertrude Stein published her first essay, marked a turning point for modern art. First created in 1902 and distributed in 1903 as a product of the Photo-Secession movement, the publication featured photogravures with text layouts based on the designs of William Morris, advertisements designed by Stieglitz and issues dedicated to prominent artists, including eventually, those outside the medium, like Picasso. “
Stieglitz’s objective, as he declared in the first issue, was to publish  “quarterly an illustrated publication which will appeal to the ever-increasing ranks of those who have faith in photography as a medium of individual expression.”
 Get the whole collection of Camera Work for $20!!!
Photographer, writer, publisher, and curator Alfred Stieglitz (1864–1946) was a visionary far ahead of his time. Around the turn of the 20th century, he founded the Photo-Secession, a progressive movement concerned with advancing the creative possibilities of photography, and by 1903 began publishing Camera Work, an avant-garde magazine devoted to voicing the ideas, both in images and words, of the Photo-Secession. Camera Work was the first photo journal whose focus was visual, rather than technical, and its illustrations were of the highest quality hand-pulled photogravure printed on Japanese tissue. 
Berenice Abbott purchases Eugène Atget’s estate:
In 1927 Berenice Abbot became the largest collector of Atget’s work when she purchased his estate. For the next forty years, Abbott devoted much of her creative life to popularizing Atget’s work. Our vision of Eugene Atget and Atget’s Paris was literally Abbott’s invention. Drawn from work in previously unpublished archives, this book details Abbott’s rare prints of Atget’s negatives for the first time.