The History of Geocaching
GPS, or Global Positioning System, was developed by the US Department of Defense. This satellite navigation system was intended for military use and therefore the signals were scrambled, limiting accuracy for civilian use to about 100 meters. On May 1, 2000, President Clinton announced that this scrambling, known as Selective Availability (SA), would be turned off. Civilians were then able to enjoy accuracy on the order of 10 meters.
On May 3, 2000, Dave Ulmer proposed a way to celebrate the demise of SA. He hid a bucket of trinkets in the woods outside Portland, Oregon and announced its location in a posting made to the USENET newsgroup sci.geo.satellite-nav. This announcement is remarkable for laying out the essence of the hobby that is still in place today. It's all there. The container. The trinkets. The log book. The rule of take something, leave something, sign the logbook. Dave Ulmer invented geocaching in one fell swoop in that newsgroup posting.