To me, the tight caps with a tiny bill are a throwback to a functional bonnet that many working women, many enslaved, wore. But others think they are an attempt to replicate a Union soldier's cap, in feminine form. Many African-American women served in various roles in the Civil War, usually as irregulars or saboteurs, not just the ones you read about in official histories, which were of course written by white men, who would ascribe their actions to any male in their group, rather than admit that women - of all races - participated.