EFnet was the first IRC network, later followed by Undernet, Dalnet, and the rest.
The history of IRC networks is not unlike the development of the Usenet newsgroups alt category, where a rebellion against over-control at the center ended up changing the landscape. In the beginning, there was only one IRC network, EFnet. As the network grew, more and more servers began joining and linking to existing servers, increasing the overall load for all. Some of the server administrators liked the openness of this approach, and placed no limitations on connections by other servers, while others wanted some control and say over the membership.
Eventually one of the admins in favour of control inserted a “Q-line” statement in their server configuration banning an open-membership server called Eris in order to draw a line in the sand, and soon others followed. Eris and others then formed a network called Anet (Anarchy Network), but without a critical user mass it eventually withered away. Nevertheless, this was the prelude to the wall giving way before the flood.
As more and more servers began to ask to join EFnet, driving up processing and Internet bandwidth requirements, the conditions for joining the network began to get more strict and so more applicants were turned away. Where there is a demand there will usually be a supply, and before long a separate network called Undernet was established, followed not long after by Dalnet, and then others as the IRC network world became a heterogeneous place.
However, there was another significant development to come, the split of EFnet itself. As the original network continued to grow, disagreements arose within its ranks over how to administrate the growing structure, including the range of rights to be assigned to channel operators. In general, supporters were divided by the U.S. border, with supports of guidelines located in Europe and elsewhere and supporters of more powers in the United States.
At the same time, there was dissatisfaction by the U.S. operators with the administrator for the main transatlantic link at irc.stealth.net, sufficient that several times they kicked his server off the network, cutting off Europe without warning. In the summer of 1996, after one of these network splits, several European operators including Vegard Engen and others who had already been lobbying for a separate network decided to use the interruption as an opportunity, and sent an email to the operator list declaring establishment of a separate network.
In the following days the shape of the two networks was solidified, with Australia and Japan joining the Europeans. While it was the smaller of the two networks compared to the U.S. based EFnet, the new network included Finland and the original Oulu site, and so they named themselves IRCnet.
Resources. The following references provide more information: