123rd Illinois Volunteer Infantry Regiment

123rd Illinois Volunteer Infantry Regiment
Illinois state flag
Active	September 6, 1862, to July 11, 1865
Country	United States
Allegiance	Union
Branch	Infantry, Mounted (1863-1864)
Engagements	Battle of Perryville Battle of Stones River (Murfreesboro II) Battle of Vaught's Hill Battle of Hoover's Gap Battle of Chickamauga Battle of Farmington Atlanta Campaign Battle of Resaca Battle of New Hope Church Battle of Dallas Battle of Marietta Battle of Kennesaw Mountain Garrard's Raid Wilson's Raid Battle of Selma

The 123rd Illinois Volunteer Infantry Regiment was an Infantry Regiment that served in the Union Army during the American Civil War. In 1863 and 1864 it was temporarily known as the Mounted Infantry, 123rd Regiment as part of Wilder's Lightning Brigade.

This regiment was organized at Camp Terry, Mattoon, Coles County, Illinois, by Colonel James Monroe, who at the time was major of the 7th Illinois Infantry. Companies A, C, D, H, I and K were from Coles County; B from Cumberland; E from Clark; F and G from Clark and Crawford. As a colonel in 1861, Ulysses S. Grant organized his first command, the 21st Illinois Volunteer Infantry Regiment, in Mattoon.

It was mustered into service on September 6, 1862, with James Monroe as Colonel, Jonathan Biggs, of Westfield, Clark County, as Lieutenant Colonel, and James A. Connolly, of Charleston, Illinois, as Major. On 19 September 1862, the Regiment was loaded into freight cars at Mattoon, and transported to Louisville, Kentucky, where it was at once put to work, under Major General William "Bull" Nelson, to fortify the city against Confederate General Braxton Bragg, who was then advancing on it in pursuit of Union General Don Carlos Buell.

On October 1, having been assigned to the Thirty-third Brigade (General William R. Terrill), Fourth Division (General James S. Jackson), in McCook's Corps, the regiment started on the march under Buell, southward through Kentucky, after Bragg, who had turned back, and up to this time the regiment never had battalion drill, and hardly an attempt at company drill, as all the officers, except the colonel, were "raw recruits".