The idea of a female entertainer becoming a "gay icon" goes back even earlier than Judy Garland - Mae West actually had this honor in the 1930s, and as she's the originator, understanding why can help to explain this tradition.

Mae West's career began in vaudeville in her early teens, and she started performing in actual musicals in the 1910s. Part of her appeal even then was her exaggerated femininity and sexuality, initially derived in part from female impersonators like Julian Eltinge, and you can see a kind of circle-influence where West took inspiration from turn-of-the-century camp, and in turn her heightened, campy style would become inspiration for drag in later years: her body was far from the feminine ideal for the 1920s and 1930s, with a fuller hourglass figure that she further enhanced with foundation garments, rather than wearing the rather flattening or at least "natural-looking" brassieres and hip-slimming girdles of the time. Her public persona was also overtly sexual, known for quips about wanting a man, being a "bad girl", falling into sin, etc. - also common to drag today.

In 1926, West wrote, directed, and starred in a play titled Sex, which centered on a sex-worker protagonist; not only did it treat her sympathetically, she ends the show happily, going off to Australia with a respectable former client. Her next, The Drag, centered on a young gay man in an unhappy marriage and featured a drag ball at the opening of the third act. (This one doesn't end happily, although the story's perspective is most sympathetic to the gay male characters.) Both were shut down and landed her in prison, which only helped to cement her reputation. She was also supportive of homosexuality/gay rights on a personal level, actively soliciting gay actors for The Drag and catering to her gay fans later in life, although in this she did bend to appease the mores of the times to some extent before the 1960s.

Judy Garland was a different kind of gay icon: she was not flamboyantly feminine, and she didn't really push boundaries in her work. Judith Peraino, in Listening to the Sirens: Musical Technologies of Queer Identity from Homer to Hedwig (2005), notes that the divorce between the entertainment property "Judy Garland" and the actual woman, Judy Garland, created an instability that "represented the conundrum of queer subjectivity". That is, the difference between the pristine version of Garland presented on movie screens and in records (created by rehearsal, costuming, and judicious editing) and the actual, messy Garland who had multiple divorces, nervous breakdowns, comebacks, and no-shows (failure to meet the expectations of the former? or deliberate resistance to it?) resembled the experience of most pre-Stonewall gay men in the closet: putting up a heterosexual front for the world at large while privately loving, suffering, and resisting. Gerald Clarke's biography, Get Happy: The Life of Judy Garland (2009), also suggests that there was identification with the jokes and contempt that mainstream society aimed at her for her messiness, much the same way they themselves were treated for their homosexuality.

Where West's visual aesthetic was a part of her attraction as an icon, Garland's aesthetic aspect was her voice, which was (and is in recordings) very expressive and emotional, and has a very distinctive sound that cannot be mistaken for any other singer. And of course, the movie that introduced her as a leading actress, The Wizard of Oz (1939), both has the potential for camp - as well as actual camp in Burt Lahr's performance as the Cowardly Lion - and easily recognizable parody, and relates to the public/private divide discussed above, with the black-and-white Kansas representing the outer world where gay men had to present a heterosexual image and the magical, technicolor Oz representing the gay scene. ("Friend of Dorothy" is for this reason an old-school euphemism for a gay man.)

In addition, she was quite liberal - she supported the Hollywood Ten in the 1940s and civil rights movements in the 1960s. She was also simply comfortable friends with gay men in a time where that was uncommon from straight (or at least, presumably straight) people, going to gay bars with them from an early age.

Many other female performers have reached this status as well, usually for similar reasons, typically including their support of gay rights and their relationships with gay fans. Cher, Madonna, and Lady Gaga, for instance, have numerous looks (and voices, particularly when it comes to Cher) that can be easily dragged into camp. Many other actresses from Garland's period also have an iconic status due to onscreen roles (like Rita Hayworth in Gilda) or to a combination of aesthetic and personal issues (like Marilyn Monroe).