It was 38 years ago today that the U.S. Patent Office officially recognized an invention that would help make computers more accessible to the masses. We are, of course, talking about Douglas Engelbart's "X-Y position indicator for a display system," more commonly known today as the computer mouse. Engelbart, 83, then a researcher at Stanford Research Institute (SRI) in Menlo Park, Calif., filed the patent in 1967 but had to wait three years for the government to acknowledge his technology, which  provided the tool needed to navigate graphics-filled computer screens with a simple motion of the hand rather than by wading through screens filled with green-tinted text using keys or a light pencil pressed up against a computer monitor.

Although largely taken for granted today, the notion of using an "X-Y position indicator" to move around a computer screen was a radical notion back then. In his patent application, Engelbart described his invention as "a mechanism comprising a small housing adapted to be held in the hand and having two wheels and an idler ball bearing for contacting the surface on which it rests." This was a sleeker design for navigating the computer screen than the "trackball," (a computer interface that allows you to control the cursor by running your fingers or palm over a ball housed in a socket containing sensors) invented by Tom Cranston, Kenyon Taylor and Fred Longstaff as part of the Royal Canadian Navy's DATAR system in 1952. The trackball is still in use today, but on a much smaller scale—Cranston and Longstaff's invention actually used a bowling ball. This original trackball and Engelbart's position indicator provide the ancestry for the modern computer interface, which can be wireless, be an optical mouse that uses a laser diode to determine position or even function in three dimensions (like the controller for Nintendo's Wii gaming system).

One would imagine that inventing something as ubiquitous as the computer mouse would have made Engelbart a rich man. But  his patent expired before it became widely used with PCs, BBC News reported—and so Engelbart garnered neither the recognition nor the royalties of his invention. Xerox Corporation was the first to sell a computer system that came with a mouse—the 8010 Star Information System in 1981, but the mouse wouldn't become a part of the modern lexicon until Apple made it standard equipment with its original Macintosh, which debuted in 1984. The emergence of Microsoft Windows and Web browsers hastened the mouse's pervasiveness throughout the 1990s.

The mouse's creation and development parallels that of the Internet. Engelbart originally invented the mouse as a way to navigate his oNLine System (NLS), a pre-cursor  of the Internet that allowed computer users to share information stored on their computers. NLS, which Engelbart developed with funding from the Defense Department's Advanced Research Projects Agency (at the time known simply as "ARPA"), was also the first system to successfully use hypertext to link files (making information available through a click of the mouse).

Mouse technology found its way from Engelbart's lab to Xerox's Palo Alto Research Center (PARC) in 1971, when Bill English, a computer engineer who had worked for Engelbart at SRI, joined PARC. Engelbart's own work at SRI came to an end in 1989, when McDonnell Douglas Corp. (a company he found himself working for after his division at SRI changed hands a few times) shut down his lab. That year, Engelbart formed the Bootstrap Institute, a consulting firm in Menlo Park, Calif., through which he encourages researchers to share findings and build on one another's  achievements.

(Images courtesy of the U.S. Patent Office)