On June 17, 1966, 19-year-old Thomas Guy Cleveland from Northridge, California, was killed while attempting to sneak into the park by climbing onto the monorail track. Ignoring a security officer's shouted warnings, he was struck by the train and dragged 30 to 40 feet down the track.

June 1966 was a pivotal month in Disneyland history, as it marked the grand opening of New Orleans Square, the first "new" land added to the park since its 1955 opening. This $18 million expansion included the debut of the Disneyland Railroad's New Orleans Square Station. While the iconic Pirates of the Caribbean wouldn't open until 1967, the thematic foundations were laid in June '66, featuring the "Blue Bayou" aesthetic. Furthermore, June 1966 saw the introduction of the "it's a small world" attraction to the park after its successful run at the 1964-65 New York World's Fair. This month also represented one of the last periods of major creative expansion overseen personally by Walt Disney, who passed away just six months later in December 1966. For historians, this month represents the transition from the "original" park to the more sophisticated, high-capacity themed environments that define the modern Disney era.