The 18th Regiment Illinois Volunteer Infantry was an 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 18th Illinois Infantry was organized at Aurora, Illinois

Aurora, Illinois

Aurora is the second most populous city in the U.S. state of Illinois, and the 112th largest city in the United States. A suburb of Chicago, located west of the Loop, its population in 2010 was 197,899. Originally founded within Kane County, Aurora's city limits have expanded greatly over the past...

 and mustered into Federal service on May 28, 1861 for a three year enlistment.

The regiment was mustered out of service on December 31, 1865.

Total strength and casualties

The regiment suffered 6 officers and 99 enlisted men who were killed in action or who died of their wounds and 7 officers and 282 enlisted men who died of disease, for a total of 394 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...
  
   Michael K. Lawler - promoted to 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 April 14, 1863.
• Colonel Daniel H. Brush - resigned August 21, 1863.
• Lieutenant Colonel
  Lieutenant colonel
  Lieutenant colonel is a rank of commissioned officer in the armies and most marine forces and some air forces of the world, typically ranking above a major and below a colonel. The rank of lieutenant colonel is often shortened to simply "colonel" in conversation and in unofficial correspondence...
  
   Samuel B Marks - resigned 1864