"Jack-A-Roe" (originally "Jack Munro") may be the world's oldest song about a cross-dresser. If not, it's certainly in the running. It could also be called a song of woman's empowerment, perhaps even one of feminism (if a listener were so inclined).
The song is best known today for being a staple of the Grateful Dead's live set, but it can be traced back definitively to early 1800s England. The oldest broadside version
, held by the Bodleian Libraries of Oxford University, is dated between 1812 and 1825. At that time, the song was titled "Jack Munro."
The song is about a young woman who dresses as a sailor in order to find her lover, Jack. She's the daughter of a wealthy merchant, yet elects to put herself in grave danger in order to get her sweetheart back. The naval men notice her slight build and question if she can succeed in battle, but she proves her mettle, finds her wounded Jack, gets him to a doctor, and marries him.
The Dead's version leaves out a bit of the traditional song's lyrics but keeps the gist of things. Nothing substantive is lost, but in some traditional variations there are more details about the central character's relationship with her father.