The 21st Regiment Illinois Volunteer Infantry was a militia

Militia (United States)

The role of militia, also known as military service and duty, in the United States is complex and has transformed over time.Spitzer, Robert J.: The Politics of Gun Control, Page 36. Chatham House Publishers, Inc., 1995. " The term militia can be used to describe any number of groups within the...

 infantry

Infantry

Infantrymen are soldiers who are specifically trained for the role of fighting on foot to engage the enemy face to face and have historically borne the brunt of the casualties of combat in wars. As the oldest branch of combat arms, they are the backbone of armies...

 regiment

Regiment

A regiment is a major tactical military unit, composed of variable numbers of batteries, squadrons or battalions, commanded by a colonel or lieutenant colonel...

 that served in the Union Army

Union Army

The Union Army was the land force that fought for the Union during the American Civil War. It was also known as the Federal Army, the U.S. Army, the Northern Army and the National Army...

 during the American Civil War

American Civil War

The American Civil War was a civil war fought in the United States of America. In response to the election of Abraham Lincoln as President of the United States, 11 southern slave states declared their secession from the United States and formed the Confederate States of America ; the other 25...

.

Service

The 21st Illinois Infantry was organized at Mattoon, Illinois

Mattoon, Illinois

Mattoon is a city in Coles County, Illinois, United States. The population was 18,555 as of the 2010 census. It is a principal city of the Charleston–Mattoon Micropolitan Statistical Area.Mattoon was the site of the "Mad Gasser" attacks of the 1940s....

 and mustered into Federal service on June 28, 1861.

The regiment was mustered out on December 16, 1865.

Total strength and casualties

The regiment suffered 1 officer and 51 enlisted men who were killed in action or who died of their wounds and 2 officers and 127 enlisted men who died of disease, for a total of 181 fatalities.

Commanders

• Colonel
  Colonel
  Colonel , abbreviated Col or COL, is a military rank of a senior commissioned officer. It or a corresponding rank exists in most armies and in many air forces; the naval equivalent rank is generally "Captain". It is also used in some police forces and other paramilitary rank structures...
  
   Ulysses S. Grant
  Ulysses S. Grant
  Ulysses S. Grant was the 18th President of the United States as well as military commander during the Civil War and post-war Reconstruction periods. Under Grant's command, the Union Army defeated the Confederate military and ended the Confederate States of America...
  
   - promoted brigadier general
  Brigadier General
  Brigadier general is a senior rank in the armed forces. It is the lowest ranking general officer in some countries, usually sitting between the ranks of colonel and major general. When appointed to a field command, a brigadier general is typically in command of a brigade consisting of around 4,000...
  
  on August 7, 1861.
• Colonel John W.S. Alexander - killed in action September 20, 1863.