The first Graphical User Interface (GUI) was developed by researchers at Xerox PARC (Palo Alto Research Center) in the 1970s. They created a system known as the Xerox Alto, which was the first computer to use a GUI. This included features like windows, icons, and a mouse for navigation, elements that have become standards in modern interfaces. While the Alto was never commercially released, it influenced many subsequent systems. The most notable of these are Apple's Macintosh and Microsoft's Windows, which popularized GUIs and made them a mainstay of personal computing.