Speaking of OS X history, here’s James Thomson on Twitter:
It’s really a weird experience rewatching Steve introducing the Dock for the first time, as it was my code that was running here. To say I was terrified for the whole length of this segment is underselling it. I don’t think I’ve seen this since.
This demo—the YouTube video is here—is from a developer preview version of OS X. Notice that when Jobs drags files into the Dock, they disappear from the Desktop! As James reminded me, they were moved into a Dock folder inside your user folder.
The Dock, though it was rewritten multiple times before OS X shipped, is one of the only NextStep interface design influences to make an impact on OS X.