The "Constitution" of the internet is contained in the RFCs.
Request for Comments cover general operation, file formats, system protocols, etc...
RFC #1 was published April 7th, 1969
From the New York Times:
How the Internet Got Its RulesWritten by Steve Crocker who was the author of RFC #1 Don't forget to check out RFC 1149
Today is an important date in the history of the Internet: the 40th anniversary of what is known as the Request for Comments. Outside the technical community, not many people know about the R.F.C.�s, but these humble documents shape the Internet�s inner workings and have played a significant role in its success.
When the R.F.C.�s were born, there wasn�t a World Wide Web. Even by the end of 1969, there was just a rudimentary network linking four computers at four research centers: the University of California, Los Angeles; the Stanford Research Institute; the University of California, Santa Barbara; and the University of Utah in Salt Lake City. The government financed the network and the hundred or fewer computer scientists who used it. It was such a small community that we all got to know one another.
A great deal of deliberation and planning had gone into the network�s underlying technology, but no one had given a lot of thought to what we would actually do with it. So, in August 1968, a handful of graduate students and staff members from the four sites began meeting intermittently, in person, to try to figure it out. (I was lucky enough to be one of the U.C.L.A. students included in these wide-ranging discussions.) It wasn�t until the next spring that we realized we should start writing down our thoughts. We thought maybe we�d put together a few temporary, informal memos on network protocols, the rules by which computers exchange information. I offered to organize our early notes.
What was supposed to be a simple chore turned out to be a nerve-racking project. Our intent was only to encourage others to chime in, but I worried we might sound as though we were making official decisions or asserting authority. In my mind, I was inciting the wrath of some prestigious professor at some phantom East Coast establishment. I was actually losing sleep over the whole thing, and when I finally tackled my first memo, which dealt with basic communication between two computers, it was in the wee hours of the morning. I had to work in a bathroom so as not to disturb the friends I was staying with, who were all asleep.
