The Americans, by Robert Frank

Why?

"All those pictures now, are still ingrained in my head. My consciousness. There's not a picture from there I wouldn't recognize. As with many other people." 
- Martin Parr, Photographer

 "It really opened up the world of documentaries for me. That in a way documentaries could have authorship, and could have subjectivity, and could have point of view, and could have commentary, and really because of perspective and the way the photographer saw it."
- Lauren Greenfield, Photographer