That would be Mary Ellen Mark. She was voted Most Influential Woman Photographer by American Photo magazine. All I can say is WOW ! Her work is awesome. I know, I use the word too much, yet her photos are, indeed, awesome.
I saw her on the Today show...when? Why, today of course. If you missed it and want to check it out, the link to msnbc's site with her interview follows below. If you have the connection, I encourage you to 'launch' the video play of the interview... you'll only have to sit thru one short commerical before it plays.
(one of these days I'll learn how to embed the links...if 'embed' is the right term.)
She has a web site: http://www.maryellenmark.com/