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23rd Regiment Illinois Volunteer Infantry
Illinois state flag
Active June 15, 1861 to July 24, 1865
Country United States
Allegiance Union
Branch Infantry

The 23rd Regiment Illinois Volunteer Infantry, known as the "Irish Brigade", was an infantry regiment that served in the Union Army during the American Civil War.


The 23rd Illinois Infantry was organized at Chicago, Illinois and mustered into Federal service on June 15, 1861.

The regiment was mustered out on July 24, 1865.

Total strength and casualties[]

The regiment suffered 4 officers and 50 enlisted men who were killed in action or who died of their wounds and 2 officers and 93 enlisted men who died of disease, for a total of 149 fatalities.[1]


  • Colonel James A. Mulligan - killed in action July 24, 1864.
  • Lieutenant Colonel Samuel Simison - mustered out with the regiment.[2]

See also[]

  • List of Illinois Civil War Units
  • Illinois in the American Civil War


  1. The Civil War Archive website after Dyer, Frederick Henry. A Compendium of the War of the Rebellion. 3 vols. New York: Thomas Yoseloff, 1959. - retrieved June 25, 2007.
  2. Illinois in the Civil War website after Illinois Adjutant General's muster rolls - retrieved June 26, 2007.


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