First one I ever saw was a bulletin board type, used by the NASA bigwigs. First one I ever used was AOL, in the early-mid 90s.
Who Invented The First Chat Room? Who Even Came Up With The Idea?
The idea of a chat room has been around since time began talking around a camp fire,meeting at the local burger joint/soda shop,yacking down at the corner store,sitting on the front porch,tv talk shows,e- mails,pen pals,party phone lines...even sites that are not chatrooms become places to yack back and forth....all someone did was define it as a chatroom, make a word up for it....now you have blogs and facebook old ideas remade to work on the internet...so I would say no one person/group can claim rights to the idea of a chat room...just my opinion
I don't think that there is any one person who can claim they invented the chat room, it is really, as Nomad1 said, this has been going on since people were sitting around campfires.