Ars Technica's Matthew Lasar has a great potted history of the 1972 first International Conference on Computer Communication in Washington, DC, where, for the first time, ARPANet (the first iteration of the Internet) was demonstrated to the public:
Monday morning October 24 arrived. Conference attendees meandered into the exhibition. One sat down at a computer, followed some instructions, and tried to access a computer that most likely wasn't operational at the moment.
"HOST DEAD," came the line response.
"Oh, my God. I've killed it!" he cried out in a panic.
Another two attendees sat down at machines and had an experience that would be shared by millions of cell phone texters three decades later. They both logged into the University of Utah host and accessed the TALK protocol.
"Where are you?" one typed.
"I'm in Washington," the other replied.
"Where?"
"At the Hilton."
"Well, I'm at the Hilton too."
They were, of course, practically sitting next to each other.