McDonald's introduced the fictional world of McDonaldland in 1971.
McDonaldland was a fantasy setting created for McDonald's advertising and merchandising. It populated the brand with characters including Ronald McDonald, the Hamburglar, Grimace, Mayor McCheese, and Birdie the Early Bird.
The setting gave McDonald's a shared story world that could support television commercials, restaurant promotions, playground themes, and licensed products. Instead of presenting the restaurant only as a place to buy food, the campaign made it part of an imaginative children's universe.
The characters changed over time, and some were retired or used less frequently. McDonaldland is therefore best understood as a branding and advertising concept, not a physical theme park or an official geographic location.