Civil War

In terms of the percentage of the male population involved, the Civil War was by far the biggest war in U.S. history. It was also the bloodiest: more Americans died than in both World Wars combined.

When the war began in April, 1861 at Fort Sumter, both Northern and Southern militia units rushed to join the Army. Both sides thought the war would be short: in the North, the first volunteers were only enlisted for 90 days. After the war's first battle, at Bull Run, it became obvious that the war would be a long one. President Lincoln called for 400,000 volunteers to serve for three years. Many militia regiments returned home, recruited and reorganized, and returned as three-year volunteer regiments.

After most of the militia, both North and South, were on active duty, each side turned to conscription. The Civil War draft law was based on the legal obligation to serve in the militia, with quotas for each state.

Many of the most famous Civil War units, from the 20th Maine which saved the Union line at Gettysburg to Stonewall Jackson's famous brigade of "foot cavalry" were militia units. The largest percentage of Civil War battle streamers are carried by units of the Army National Guard. After the end of the Civil War, the South was under military occupation. Under Reconstruction, a state's right to organize its militia was suspended, to be returned only when that state had an acceptable Republican government. Many African-Americans joined the militia units formed by these governments. The end of Reconstruction in 1877 brought the militia back to white control, but black militia units survived in Alabama, North Carolina, Tennessee, Virginia, and five Northern states.

In all sections of the country, the late 19th century was a period of growth for the militia. Labor unrest in the industrializing Northeast and Midwest caused those states to examine their need for a military force. In many states large and elaborate armories, often built to resemble medieval castles, were constructed to house militia units.

It was also during this period that many states began to rename their militia "National Guard". The name was first adopted before the Civil War by New York State's militia in honor of the Marquis de Lafayette, hero of the American Revolution, who commanded the "Garde Nationale" in the early days of the French Revolution.

In 1889, after the U.S. battleship Maine blew up in the harbor of Havana, Cuba, the U.S. declared war on Spain (Cuba was a Spanish colony). Because it was decided that the President did not have the right to send the National Guard outside the United States, Guard units volunteered as individuals - but then reelected their officers and remained together.