GPS was actually created by the US Department of Defense as a satellite navigation system intended only for military use; so, the DOD would scramble signals, limiting accuracy for civilian use to only about 300 feet (imagine geocaching with that kind of accuracy!). 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 30 feet.
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, signing the logbook. Dave Ulmer invented geocaching in one fell swoop in that newsgroup posting. Within a day, the original stash had been found. Within days, more stashes were hidden in California, Kansas, and Illinois. Within a month, a stash was hidden as far away as Australia...