Just for historical accuracy, this doesn’t predate the Internet, it’s just before you were on the Internet. The Internet came into being on DARPANET circa 1973 and Usenet appeared in 1979. So, according to astro’s links, the first BBSs came after the Internet but beat Usenet by a year.
Back at college (Brandeis, mid-80s), there were quite a few lively discussions on the public restroom walls.
I get a nostalgic feeling every time I wander into MPSIMS. 
I inherited a bunch of my family’s letter stashes. Many of my recent forebears would wrote letters that included a wad of clippings from newspapers and magazines.
A fair mention should also go to samizdat(?), the newsletters put out by Soviet dissidents. It’s hard to imagine a world where photocopiers were rare and closely monitored, where some countries typewriters had to be registered with the police and type samples were kept on file with the police. Dissidents would type up newsletters (blogs?) and then circulate them from hand to hand.
It’s pretty hard to get more historical than the cathedral doors in Wittenberg, Germany, 500 years ago. Most people today don’t realize that Martin Luther wasn’t doing anything out of the ordinary by posting his 95 theses.
There were similarly Corresponding Societies in the UK.
And anyone who’s ever had to see an institutionalor communal noticeboard (of the old analogue kind) will know they soon include a fair few “conversations” of added messages.
Before Tienanmen and in other times of turmoil in China, there were noticeboard “newspapers” that also became the locus for written debates, and (I don’t doubt) in other countries too.
And don’t forget graffiti…
Yep, going way way back, the Graffiti found at Pompeii is strangely reminiscent of many internet forums only with more creative insults.
http://www.pompeiana.org/Resources/Ancient/Graffiti%20from%20Pompeii.htm
A “Circle Letter” was a fair approximation.
A group of friends or family would send one package of letters from one to another according to a set list.
When the circle letter arrived, you read all the letters from each participant, then replaced your old letter with a new one, bundled up the whole batch, and sent it on to the next person on the list.
My parents used these to keep in touch with their siblings and parents. My cousins started one, but I am off the list because my mom gave them an obsolete address for me, and the circle letter went off to oblivion.
They’re still used that way; some of my local parishes have a corkboard outside as well as the doors, some don’t, but in any case board and doors are used to post funeral notices, wedding bans, church announcements, posters from NGOs ranging from the local Humane Society to the Scouts…
From the first lined article.
I used PLATO starting in 1974, and PAD was pretty much indistinguishable from the SDMB. Including quoting. When quoting was introduced, there was a long thread which consisted of “Don’t you get a feeling of deja vu reading Pad?” quoted and quoted and quoted 30 or 40 deep.
A shared story which began “it was a dark and stormy night” broke the system as it got more responses than allowed.
Pad quickly split into pads for specific topics - such as religion - long before UNIX news was developed.
PLATO also had chat rooms, instant messaging (term-talk) and MUDs. And each PLATO terminal had a plasma panel with touch capabiloty used in TUTOR lessons (PLATO for programs.) It also had a newspaper where I had a Star Trek column.
As far as deep history goes, I’ve not read at the Talmud, but my impression is that it has some message board like characteristics in that writers commented both on the text and on the responses of others.
That’s where the words of the prophets are written.
In Jr High, we had what we called “slang books”. You took a note book, wrote each person’s name at the top of a given page, circulate and comment. Cruel beyond imagination…
This was the first thing that came to my mind, as well. (Although, as noted below, cork bulletin boards did not support comments).
I remember one on my college campus, that was for ride-sharing “going to Santa Barbara Fri 10/21 – you pay for gas”. So in this way, it functioned like craigslist.
In college we had one in the locker room - but more like the. BBQ Pit - with pictures!
Cartoonacy writes:
> Amateur Press Associations.
See post #12.
John Mace writes:
> In Jr High, we had what we called “slang books”.
Interesting. I’ve only heard them called slam books. That seems to be the more common name based on some online searches I’ve just done. It also makes more sense as the original name, since it implies that it’s about slamming people.
Cave paintings?
While Notes & Queries was one of the most popular of these English periodicals, there were others that also had little flame wars and grandiose pronouncements going on in the letters sections. The Gentleman’s Magazine, Archaeologia, and the Proceedings of the Society of Antiquaries of London are some of the larger ones, but many smaller journals also circulated, such as the Transactions of the London and Middlesex Archaeological Society and the Proceedings of the Suffolk Institute of Archaeology.