12th Illinois Infantry (3 years) in the American Civil War

Overview

The 12th Illinois Infantry (3 years) was an infantry regiment from Illinois that served in the Union Army during the American Civil War. Organized at Cairo, Illinois, the regiment was mustered into United States service for a three-year term on August 1, 1861. The unit participated in major campaigns in the Western and Southern theaters, including operations in Kentucky, Tennessee, Mississippi, Georgia, and the Carolinas. The 12th Illinois Infantry is noted for its early occupation of Paducah, Kentucky, and for its involvement in several significant battles and campaigns throughout the war.

This regiment is distinct from any earlier or later units with similar designations or different service terms.

Organization & Service

The 12th Illinois Infantry (3 years) was organized at Cairo, Illinois, and mustered into service on August 1, 1861. The regiment remained at Cairo until September 5, 1861, when it, alongside the 9th Illinois Infantry, moved to occupy Paducah, Kentucky, becoming the first Union troops to enter the city. Four companies were detached to Smithland, Kentucky, where they remained until January 25, 1862, and participated in demonstrations against Columbus, Kentucky, during the Battle of Belmont.

The regiment joined the movement against Fort Donelson in February 1862 as part of McArthur’s Brigade, which included the 9th and 41st Illinois Infantry. The 12th Illinois suffered significant casualties during the assault on February 15. It subsequently fought at the Battle of Shiloh in April 1862, engaging nearly continuously over two days. Following Shiloh, the regiment participated in the advance on and siege of Corinth, Mississippi, performing picket and fatigue duties and extending saps. After the evacuation of Corinth, the unit joined General Pope in pursuit of Confederate forces and later fought in the Battle of Corinth in October 1862, where it played a prominent role in retaking works and capturing enemy colors and artillery.

In April 1863, the regiment was dispatched to reinforce Glendale, Mississippi, but the engagement concluded before its arrival. On January 16, 1864, the men reenlisted as veterans and were granted a furlough at Camp Butler, Illinois. Returning to the field, the regiment participated in the Atlanta Campaign from May 1864, remaining active through the fall of Atlanta. In October, the regiment fought at Allatoona, suffering heavy losses. The 12th Illinois then joined Sherman’s March to the Sea, passing through several Georgia towns and encountering minor opposition. In early 1865, the regiment took part in the Carolinas Campaign, including the Battle of Bentonville. After the surrender of Johnston’s army, the regiment marched through Virginia, participated in the Grand Review in Washington, D.C., and was mustered out at Louisville, Kentucky, on July 10, 1865.

Engagements & Campaigns

• Occupation of Paducah, Kentucky (September 1861)
• Demonstration against Columbus, Kentucky (November 1861)
• Fort Donelson (February 1862)
• Battle of Shiloh (April 1862)
• Siege of Corinth (April–May 1862)
• Pursuit after evacuation of Corinth (May 1862)
• Battle of Corinth (October 1862)
• Defense of Glendale, Mississippi (April 1863)
• Atlanta Campaign (May–September 1864)
• Battle of Allatoona (October 1864)
• Sherman’s March to the Sea (November–December 1864)
• Carolinas Campaign (early 1865)
• Battle of Bentonville (March 1865)

Casualties

• Fort Donelson: 19 killed, 58 wounded, 10 missing
• Shiloh: 109 killed and wounded, 7 missing
• Corinth (October 1862): 17 killed, 80 wounded, 15 missing
• Allatoona: 57 killed and wounded
• Bentonville: 2 wounded

Total losses for the regiment are not fully detailed in available primary sources.

Field Officers & Commanders

• Colonel John McArthur
• Colonel Augustus L. Chetlain
• Lieutenant Colonel Augustus L. Chetlain
• Lieutenant Colonel Arthur C. Ducat
• Lieutenant Colonel Henry Van Sellar
• Major William D. Williams
• Major Arthur C. Ducat
• Major James R. Hugunin
• Major Wheelock S. Merriman

Regimental Roster

The complete roster of soldiers who served in the 12th Illinois Infantry (3 years) is available for genealogical and historical research. This roster includes names, ranks, and other service details as recorded in official state and federal records.

To view the full roster, visit the 12th Illinois Infantry (3 years) Roster page.

Sources & References

• Official Records of the Union and Confederate Armies, Series I, Volumes 7, 10, 17, 24, 38
• Report of the Adjutant General of the State of Illinois
• Dyer, Frederick H. “A Compendium of the War of the Rebellion”
• Fox, William F. “Regimental Losses in the American Civil War”
• Contemporary reports and regimental histories as cited in state records