Judy Garland is probably the greatest of the diva entertainers turned gay icons. What makes her gay legacy unique is that her "Over the Rainbow" number was released in the classic family film The Wizard of Oz in 1939. During a time when being openly gay was completely condemned, Garland's performances and personal struggles resonated with gay men. She was wildly popular during her prime and through her comebacks, and she remains a gay icon long after her death in 1969.
Interestingly, it's not just the hearts of gay men that Julie Andrews has claimed; she's a family icon as well. It kind of makes sense, given that her classic movie musicals Marry Poppins (1964) and The Sound of Music (1965) have been entertaining both demographics for generations.