Who was Vivian Maier? Many people know her as the reclusive Chicago nanny who wandered the city for decades, constantly snapping photographs, which were unseen until they were discovered in a seemingly abandoned storage locker. They revealed her to be an inadvertent master of twentieth-century American street photography. Not long after, the news broke that Maier had recently died and had no surviving relatives. Soon the whole world knew about her preternatural work, shooting her to stardom almost overnight.

But, as Pamela Bannos reveals in this meticulous and passionate biography, this story of the nanny savant has blinded us to Maier's true achievements, as well as her intentions. Most important, Bannos argues, Maier was not a nanny who moonlighted as a photographer; she was a photographer who supported herself as a nanny. In Vivian Maier: A Photographer's Life and Afterlife, Bannos contrasts Maier's life with the mythology that strangers—mostly the men...