Women were not legally allowed to fight in the Civil War, but it is estimated that 400 women disguised themselves as men and went to war.
At the time women were not considered equals to men. Women were confined to the domestic sphere. The Union and Confederate armies forbade the enlistment of women.
Women were able to enlist because the physical exams were not very rigorous. Women didn’t seem any less manly than the teenage boys who were enlisting. Women bound their breasts, wore loose clothing, cut their hair short and rubbed dirt on their faces.
When women were discovered, in most cases they were sent home. They were often found out if they were injured or became sick. There is some evidence that some women soldiers were briefly imprisoned.
Most women joined the war for the same reason as men—Patriotism, supporting their respective causes, for adventure, and to be able to leave home and earn money. They women were mostly young and often poor and from farming families.
The women did everything that men did. They worked as scouts, spies, prison guards, cooks, nurses and they fought in combat.
Source: The Women Who Fought in the Civil War