Courtesy Robert Altman
Black Panthers rally at the San Francisco Federal Building in May 1969.
It's been more than 40 years since the "counter culture" came of age in America. Long hair, psychedelic drugs, experimental rock music, and the ubiquitous peace sign were part of the landscape.
Photographer Robert Altman did as much as anyone could to preserve it by capturing the hippies on camera.
His pictures are all compiled in a new book titled The Sixties.