These two photographs show the same unidentified Black woman.
On the left she is dressed in civilian clothes.
On the right she is dressed in a Union soldier's uniform,
c.1861.
Source: New-York Historical Society Library.
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Historians have identified about 400 women who disguised themselves as men and enlisted to fight in the American Civil War. They found army records of soldiers who were discovered to be women during their service.

Historians also found pension cases for women who revealed themselves after the war ended. It is possible that the number of women soldiers was much higher, since historians only have records for those who were discovered or revealed themselves.

After the war, not every person assigned female at birth returned to life as a woman. Albert D. J. Cashier took the opportunity to establish a new identity as a male citizen. The medical doctor of his unit saw no reason to out a citizen who performed their duty admirably and kept Albert’s transition a secret from the rest of his unit.

These two photographs depict the same Black woman in and out of Union soldier dress. The photos are included in an album presented to Major M.S. Euan, but there is no identifying information about the subject, or where and why she fought.

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Source:
Women Soldiers
Photographs of women who disguised themselves as men to fight during the Civil War.

https://wams.nyhistory.org/a-na.../civil-war/women-soldiers/