21st Illinois Infantry Regiment

After its companies rendezvoused at Mattoon on May 9, 1861, the regiment was mustered into state service for a 30-day term by Captain Ulysses S. Grant on May 15.

[1] The regiment was mustered into Federal service for a term of three years as the 21st Illinois Infantry on June 28, 1861, with Grant as its colonel.

Grant was promoted to brigadier general and became commander of the District of Southeast Missouri on 7 August, being replaced by regimental lieutenant colonel John W.S.

As a result of the latter, it was transferred to Steele's Command of the Army of Southeast Missouri, and between March 31 and April 21 moved to Doniphan and thence to Pocahontas, Arkansas.

It then went to Cape Girardeau, Missouri between May 10 and 21 and Hamburg Landing between May 21 and 24, transferring to the 2nd Brigade of the 4th Division of the Army of the Mississippi during the month.

During the Battle of Chickamauga, by 2:00 p.m. on 19 September, Carlin placed the 21st Illinois in reserve 100 yards behind the 81st Indiana, which held positions in the eastern part of the Viniard Field.