Vivian Maier (1926-2009) was a nanny and amateur street photographer whose photographs never saw the light of day during her lifetime. They were discovered by real estate agent John Maloof in 2007 when he bought a suitcase of old negatives at an auction, and he later bought the rest of them when they, too, surfaced at auction, around 100,000 negatives in total. She died shortly after this discovery, without ever knowing what an impact her images would have on people in the art world. Her work shows a lot of the glamour and grit of New York, Chicago, and elsewhere that she went on her travels (throughout parts of Europe and Africa).
Her former charges have divulged as much as is known about Maier, describing her as reclusive and eccentric, but I love how they also describe her as a kind of Mary Poppins figure, because she would take them on these wild adventures but was probably somewhat proper from her French upbringing.
Self-Portraits:
On the Streets of New York City:
And Chicago:
And Canada:
all images from http://www.vivianmaier.com/