The Department of Public Health says a county resident with a confirmed case of measles visited the theme park on Oct. 16 from 9:15 a.m. to 8:35 p.m.
Earlier that morning, the person was at a Starbucks on the west side of Los Angeles.
Health officials says anyone who was at those locations at those times may be at risk of developing measles for up to 21 days.
Those people should check their medical records to determine if they were immunized or had measles previously.
There have 19 measles cases among Los Angeles County residents in 2019 and 11 cases among non-residents who traveled through.