| Unit Name: | 31st Regiment Illinois Volunteer Infantry |
| Dates: | September 18, 1861, to July 24, 1865 |
| Country: | United States |
| Allegiance: | Union |
| Branch: | Infantry, |
| Battles: | Battle of Belmont Battle of Fort Donelson Battle of Champion Hill Battle of Big Black River Siege of Vicksburg Battle of Kennesaw Mountain Battle of Atlanta Battle of Jonesboro March to the Sea |
The 31st Regiment Illinois Volunteer Infantry, nicknamed the "Dirty-First," was an infantry regiment that served in the Union Army during the American Civil War.
The 31st Illinois Infantry was organized at Jacksonville, Illinois and mustered into Federal service at Cairo, Illinois, on September 18, 1861. Among the early officers was Major Andrew J. Kuykendall, later a U.S. Representative and Illinois State Senator.
The regiment was mustered out on July 19, 1865, and discharged at Springfield, Illinois, on July 31, 1865.
The regiment suffered 9 officers and 166 enlisted men who were killed in action or who died of their wounds and 1 officer and 293 enlisted men who died of disease, for a total of 471 fatalities.[1]