PLATO is notable for being the origin of the of the computer role playing game. The history of early CRPGs is murky, because PLATO was intended for educational use and games programmers had to work in secret to avoid the administrators deleting their work, but it's possible that the first ever CRPG was the Reginald Rutherford's 1975 game "The Dungeon" (a.k.a. "pedit5" after its inconspicuous lesson name). The Dungeon was probably earlier than the lost game "m199h" that was previously thought to be first. These early CRPGs are all influenced by Dungeons and Dragons, which was first published in 1974.
The Dungeon is still playable today. The CRPG Addict blog has details:
And not only the beginnings of the CRPG. The 1977 PLATO game Oubliette definitely was the model for the 1981 Apple II/C64 (and later NES) gane Wizardry and the later games like The Bard's Tale and Might & Magic.
Well Wizardry was written by two PLATO gamers at Cornell, a university that had a PLATO terminal or two connected to the U of I system. Very much inspired by PLATO games like Oubliette and Avatar.
The Dungeon is still playable today. The CRPG Addict blog has details:
http://crpgaddict.blogspot.com/2019/01/revisiting-dungeon-19...
And more information about lost games:
http://crpgaddict.blogspot.com/2021/06/brief-everything-we-k...