What group of people were allowed to join the Union Army?

Initially, the Union Army primarily comprised white male citizens, but as the Civil War progressed, enlistment policies changed to include free Black men and eventually escaped slaves. The Militia Act of 1862 allowed Black soldiers to serve, and by the war's end, approximately 180,000 Black men had joined the Union Army. Women also played vital roles, serving as nurses, spies, and in other support capacities, although they were not officially enlisted as soldiers.