Gertrude Käsebier was a leading member of the pioneering photographic known as Pictorialism, which emphasized a subjective, painterly approach to photography rather than a documentary one.  

Though she had long been interested in art, Käsebier only began her formal training at the Pratt Institute after her children entered high school. She planned to be a painter, but eventually switched to photography. Following classes in Paris and apprenticeships with a German photographic chemist, and a Brooklyn portrait photographer, Käsebier opened her own portrait studio in 1897.
FROM https://nmwa.org/art/artists/gertrude-kasebier/

Stieglitz included Käsebier as a founding member of the Photo-Secession, a group that argued for a more natural, less manipulated photograph. In 1899, he published five of her photos, declaring her “beyond dispute, the leading artistic portrait photographer of the day.”
FROM http://www.imaging-resource.com/news/2012/05/12/nearly-forgotten-mother-of-modern-american-photography-gertrude-kaeseb

Library of Congress Biographical Essay: http://www.loc.gov/rr/print/coll/womphotoj/kasebieressay.html
Library of Congress Online Catalog: http://www.loc.gov/pictures/related/?fi=name&q=K%C3%A4sebier%2C%20Gertrude%2C%201852-1934
Shorpy Photo Gallery: http://www.shorpy.com/gertrude-kasebier-photographs