The resort was the brainchild of Walt Disney himself, but he died four years before the park opened. His brother, Roy Disney, came out of retirement to oversee the construction of the park and presided over the official opening.

When Walt Disney passed away on December 15, 1966, the physical construction of Walt Disney World in Florida had not yet truly begun. At the time of his death, the project was primarily in the land acquisition and master planning phases. Walt had successfully used "shell companies" to buy up over 27,000 acres of swamp and scrubland near Orlando, and he had just filmed the famous "EPCOT film" in October 1966 to pitch his vision to investors. The only "construction" that had occurred was the drainage of the land and the initial carving of the massive canal systems by the Reedy Creek Improvement District. It was Walt’s brother, Roy O. Disney, who came out of retirement to oversee the actual physical building of the Magic Kingdom, which didn't open until October 1, 1971. In 2026, historians often note that while Walt never saw a single brick laid, his "Project X" was so meticulously planned in his final months that his team was able to execute his vision for the Magic Kingdom with remarkable fidelity after he was gone.