Born in 1857, sharing his infancy with that of photography's, Atget left an indelible imprint on the history of photography without ever apparently having any intention of doing so. He never cultivated followers or expressed any philosophy about photography or art, but serious photographers that came after him are almost all followers who honor his aesthetic in picture making.
A sailor, an actor who lost his voice and a failed painter first, Eugene Atget didn't take up the art that made him a legend until he was forty, but over the next thirty years, shooting in and around Paris with an out of style camera and obsolete technique, he amassed an unmatched historical record of pictures.
(Photo credit; wikimedia.org, Creative Commons license)
A favorite story I heard was told by a friend of mine who was helping curate an Atget retrospective at the International Center of Photography in New York. Working through the thousands of pictures printed by Atget, he saw notes like this on the back of some: "This is now gone."
What Atget had done, unintentionally as far as we know, was preserve a visual record of a world being quickly eaten up by modernization.