In December 2014, a measles outbreak originated in Disneyland in Orange County, California and subsequently spread to other Californian counties until the epidemic was declared over in April 2015. Curiously, the outbreak affected more adults than babies and children, who are usually more susceptible to contracting vaccine-preventable diseases because they can be too young to be immunized against them. In total, 136 measles cases were confirmed in California, and 56% of these cases consisted of adults over the age of twenty years old. This map visualizes the correlation between the amount of adults living in Californian counties and where the outbreaks took place, and it seeks to tell the story of why more adults were affected by the Disneyland measles outbreak.