The 6th Indiana Infantry Regiment was an infantry regiment from the State of Indiana that served in the Union Army during the American Civil War. This regiment was the senior Indiana regiment of the Civil War, as it was numbered first in sequence after the five Indiana volunteer regiments which had served in the Mexican–American War. The regiment was originally mustered-in for a three-month period of service between April and August 1861, but after its initial term of service had expired it was re-formed in September 1861 for a further three-year period, before being mustered out in September 1864. Service The companies of the 6th Indiana Volunteer Infantry were raised in different parts of the state and organized at Indianapolis, Indiana between April 22 and April 27, 1861. The companies' counties of origin included Jefferson, Bartholomew, Daviess, Howard, Henry, Jennings, Jackson, and Hamilton. The Regiment was officially mustered into United States service for a period of three months on April 25, 1861. On the May 30, 1861, the regiment left Indianapolis, by way of Cincinnati, Ohio, for Grafton, Virginia (now West Virginia). Sent on to the town of Webster, they arrived on June 2 and marched that same night to Philippi. On the morning of June 3, the 6th Indiana participated in the Battle of Philippi, one of the first land battles of the Civil War. They later participated in the Rich Mountain Campaign. The regiment mustered out of service on August 2, 1861. Among its line officers was Captain Jeremiah C. Sullivan, who would later rise to the rank of brigadier general. The 6th Indiana Volunteer Infantry was re-enlisted for three year service from the original regiment at Madison, Indiana, on September 20, 1861, by Colonel Thomas Turpin Crittenden. The regiment subsequently fought in the Battle of Shiloh, the Battle of Stones River, the Battle of Chickamauga, and the Battle of Resaca. At the conclusion of its three-year enlistment, the regiment was mustered out of service on September 22, 1864. Soldiers of the regiment who had unexpired enlistments, and those who re-enlisted were transferred to 68th Indiana Infantry Regiment. Total strength and casualties The total strength of the 6th Indiana Infantry at the time of its organization in April 1861 was 782 men, including 37 commissioned officers. During its first three-month period of service, the regiment suffered no casualties in battle, but three enlisted men died of disease and