Colossal Cave Adventure 9+

There were other text computer games before Adventure, such as STARTREK and WUMPUS, but this was the first of its kind; the first text "interactive fiction" game. It may seem outdated and quaint by today's standards, sort of like seeing the Wright brothers' original flyer parked next to a Boeing 747, but many of us remember it fondly.

The Origins of Adventure
«I had been involved in a non-computer role-playing game called Dungeons and Dragons at the time, and also I had been actively exploring in caves — Mammoth Cave in Kentucky in particular.
Suddenly, I got involved in a divorce, and that left me a bit pulled apart in various ways. In particular I was missing my kids.
Also the caving had stopped, because that had become awkward, so I decided I would fool around and write a program that was a re-creation in fantasy of my caving, and also would be a game for the kids, and perhaps some aspects of the Dungeons and Dragons that I had been playing.
My idea was that it would be a computer game that would not be intimidating to non-computer people, and that was one of the reasons why I made it so that the player directs the game with natural language input, instead of more standardized commands. My kids thought it was a lot of fun.»

— William Crowther