| |
|---|---|
 Illinois state flag | |
| Active | June 15, 1861, to July 24, 1865 |
| Country | United States |
| Allegiance | Union |
| Branch | Infantry |
| Engagements | Siege of Lexington  Relief of Clarksburg Relief of Parkersburg Relief of Moorefield Pursuit of Lee Hedgesville and Back Creek Kanawha Valley Hampshire and Hardy Counties, West Virginia Scout to Moorefield Raid on Baltimore and Ohio Railroad Sheridan's Shenandoah Valley Campaign Second Battle of Kernstown Third Battle of Winchester Siege of Petersburg Assault on Ft Gregg-Fall of Petersburg Appomattox Campaign Surrender of the Army of Northern Virginia |
The 23rd Illinois Volunteer Infantry Regiment, known as the "First Irish" or "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.
Initially assigned to garrison the town of Lexington, Missouri, the regiment surrendered to a much larger force of pro-secession Missouri State Guard commanded by State Guard Major General Sterling Price at the Siege of Lexington in September 1861. After being paroled, General John C. Fremont (commanding the Department of Missouri) had the 23rd Illinois mustered out of service, but in December General George McClellan (now supreme commander in chief of all Union armies) had it restored.
After being reconstituted, the regiment left camp in the spring of 1862 for western Virginia, where it spent most of the rest of the war stationed there. In 1864, it joined General Philip Sheridan's army in the Valley Campaign. At the end of the year, the 23rd headed to the Richmond area for the Siege of Petersburg and was present at Appomattox.
The regiment was mustered out on July 24, 1865.