If you haven't heard about Vivian Maier, you definitely have to check out her story, although there is no much information available.
She was a French girl who came to Chicago in the early 1930's, seems that she had not a family or they had no strong bounds. It seems that she had no formal education, could barely write (in French). She worked most of her life as a nanny, among other little jobs. But her passion has the photography. She took around 100,000 pictures, which she left on her unpaid flat when she got old and sick. The boxes containing the films were sold in an auction, a young guy called John Maloof found them and started checking them. And it is one of the most vast and incredible treasures of street photography, covering many decades. At some point, Maloof -- who had no idea about photography -- got very curious about this woman, googled her and found out that she had died a few days before. (For more details, see this video.)
I made a selection of the 'Sleeping Beauties' she found in Chicago, California and elsewhere. And am afraid that she is getting on my personal ranking as high as her countryman Cartier-Bresson. I just love her work!