On May 3, 1978, the first unsolicited bulk email, or "spam", was sent by a Digital Equipment Corporation marketing representative to every ARPANET address on the west coast of the United States. ARPANET was a Department of Defense network, and the predecessor of the internet. Although it was not referred to as "spam" at the time, this event preceded the arrival of trillions of spam messages in email inboxes around the world. You can read more current articles about spam on the website CNET. The link to this site is also available through MPL's website.
If you would like to read more about the historical aspects of this infamous computer concept, try reading Brian McWilliams Spam Kings.