Ran across this old folklore.org post, thought you might enjoy it.
Andy Hertzfeld, member of the original Macintosh team:
The Macintosh User Interface wasn’t designed all at once; it was actually the result of almost five years of experimentation and development at Apple, starting with graphics routines that Bill Atkinson began writing for Lisa in late 1978. Like any evolutionary process, there were lots of false starts and blind alleys along the way. It’s a shame that these tend to be lost to history, since there is a lot that we can learn from them.
Fortunately, the main developer of the user interface, Bill Atkinson, was an avid, lifelong photographer, and he had the foresight to document the incremental development of the Lisa User Interface (which more or less became the Mac UI after a few tweaks) with a series of photographs. He kept a Polaroid camera by his computer, and took a snapshot each time the user interface reached a new milestone, which he collected in a loose-leaf notebook. I’m excited to be able to reproduce and annotate them here, since they offer a fascinating, behind the scenes glimpse of how the Mac’s breakthrough user interface was crafted.
Follow the headline link, dig in. This is historic stuff.