The Union had twenty-two million people living in its states. Of those twenty-two million, four million were men aged fifteen to forty, the age for enlistment in the military at the beginning of the Civil War. Beginning in 1863, the Union began enlisting blacks into the military.
Economically, the North changed into a booming war production center. The Civil War stimulated manufacture and agriculture. Coal, iron and steel, weapons, shoes, and woolen clothing increased dramatically. The main revenue of the North was received through taxes and money borrowed through the sell of war bonds.