Greyhawk began as Gygax's personal D&D campaign setting, used for his own games with friends and family. It was initially loosely defined and evolved over time based on gameplay.

Greyhawk was first made available to the public in the D&D supplement 'Greyhawk' (Supplement I), providing a basic overview of the world and its key locations.

Greyhawk was further developed through various adventure modules, articles in Dragon magazine, and eventually the 'World of Greyhawk' boxed set, which provided a comprehensive gazetteer of the setting.

Greyhawk remains one of the most popular and influential D&D campaign settings, inspiring countless adventures, novels, and other creative works. Many players and Dungeon Masters still use and adapt Greyhawk for their own games.