Do you ever look at your computer's screen and think, “How on Earth did we get here?” Windows, Mac, GNOME, KDE and Ubuntu's Unity are all born from a common history of desktop environment design stretching back to the 1960's. Let's take a visual voyage from the very beginning right up to the present, looking at the “1.0” releases – those very first versions – of the Desktop Environments and graphical computing platforms that made the biggest impact. (Or, at the very least, that I thought were coolest.)
In the interest of time, we aren't going to hit all of the early graphical systems here. Some very noteworthy systems, such as IBM's GDDM (and plenty of others), have been left out.