Alfred Stieglitz (1864–1946) was an American photographer and gallerist who, more than anyone, made photography accepted as a fine art. Trained in Berlin, he returned to New York and photographed the modern city — streetcars in snow, a train yard, the Flatiron Building — with the care of a painter. He founded the Photo-Secession, edited the journal Camera Work and, at his gallery 291, showed both photographers and the European avant-garde of Picasso, Matisse and Rodin. His long portrait of the painter Georgia O'Keeffe, whom he later married, ran to hundreds of photographs.
Portrait: Gertrude Käsebier, 1902 · National Gallery of Art, Washington · CC0, via Wikimedia Commons