The Good Lord Bird by James McBride

A work of fiction, the protagonist is one Henry Shackleford, a "coloured" man "liberated" by John Brown, the famous Abolitionist and activist. In an odd development, John Brown comes to believe that "Henry," a petite young man, is actually a girl and renames him "Henrietta," which masquerade "Henry" adopts with more or less equanimity.